diff --git a/Source/Core/Core/CMakeLists.txt b/Source/Core/Core/CMakeLists.txt
index 33a97d05e7..701e905869 100644
--- a/Source/Core/Core/CMakeLists.txt
+++ b/Source/Core/Core/CMakeLists.txt
@@ -304,6 +304,8 @@ add_library(core
   HW/WiimoteEmu/EmuSubroutines.cpp
   HW/WiimoteEmu/Encryption.cpp
   HW/WiimoteEmu/Encryption.h
+  HW/WiimoteEmu/Extension/BalanceBoard.cpp
+  HW/WiimoteEmu/Extension/BalanceBoard.h
   HW/WiimoteEmu/Extension/Classic.cpp
   HW/WiimoteEmu/Extension/Classic.h
   HW/WiimoteEmu/Extension/DesiredExtensionState.h
diff --git a/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.cpp b/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.cpp
index 0293ae41e4..630fa88c6f 100644
--- a/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.cpp
+++ b/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.cpp
@@ -117,7 +117,7 @@ SerializedWiimoteState SerializeDesiredState(const DesiredWiimoteState& state)
           using T = std::decay_t<decltype(arg)>;
           if constexpr (!std::is_same_v<std::monostate, T>)
           {
-            static_assert(sizeof(arg) <= 6);
+            static_assert(sizeof(arg) <= 12);
             static_assert(std::is_trivially_copyable_v<T>);
             std::memcpy(&s.data[s.length], &arg, sizeof(arg));
             s.length += sizeof(arg);
@@ -213,6 +213,9 @@ bool DeserializeDesiredState(DesiredWiimoteState* state, const SerializedWiimote
     case ExtensionNumber::SHINKANSEN:
       s += sizeof(Shinkansen::DesiredState);
       break;
+    case ExtensionNumber::BALANCE_BOARD:
+      s += sizeof(BalanceBoardExt::DataFormat);
+      break;
     default:
       break;
     }
@@ -319,6 +322,8 @@ bool DeserializeDesiredState(DesiredWiimoteState* state, const SerializedWiimote
     return DeserializeExtensionState<TaTaCon::DataFormat>(state, serialized, pos);
   case ExtensionNumber::SHINKANSEN:
     return DeserializeExtensionState<Shinkansen::DesiredState>(state, serialized, pos);
+  case ExtensionNumber::BALANCE_BOARD:
+    return DeserializeExtensionState<BalanceBoardExt::DataFormat>(state, serialized, pos);
   default:
     break;
   }
diff --git a/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.h b/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.h
index 6ef25675f3..5a7f3c99c3 100644
--- a/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.h
+++ b/Source/Core/Core/HW/WiimoteEmu/DesiredWiimoteState.h
@@ -35,7 +35,7 @@ struct DesiredWiimoteState
 struct SerializedWiimoteState
 {
   u8 length;
-  std::array<u8, 30> data;  // 18 bytes Wiimote, 6 bytes MotionPlus, 6 bytes Extension
+  std::array<u8, 36> data;  // 18 bytes Wiimote, 6 bytes MotionPlus, 12 bytes Extension
 };
 
 SerializedWiimoteState SerializeDesiredState(const DesiredWiimoteState& state);
diff --git a/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp b/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp
index 9d354a4b8e..c77622e534 100644
--- a/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp
+++ b/Source/Core/Core/HW/WiimoteEmu/EmuSubroutines.cpp
@@ -149,7 +149,18 @@ void Wiimote::HandleExtensionSwap(ExtensionNumber desired_extension_number,
   if (WIIMOTE_BALANCE_BOARD == m_index)
   {
     // Prevent M+ or anything else silly from being attached to a balance board.
-    // In the future if we support an emulated balance board we can force the BB "extension" here.
+    if (m_is_motion_plus_attached)
+    {
+      m_is_motion_plus_attached = false;
+      m_motion_plus.GetExtPort().AttachExtension(GetNoneExtension());
+    }
+    // Also force the BB "extension".
+    if (m_active_extension != ExtensionNumber::BALANCE_BOARD)
+    {
+      m_active_extension = ExtensionNumber::BALANCE_BOARD;
+      m_extension_port.AttachExtension(GetActiveExtension());
+      GetActiveExtension()->Reset();
+    }
     return;
   }
 
diff --git a/Source/Core/Core/HW/WiimoteEmu/Extension/BalanceBoard.cpp b/Source/Core/Core/HW/WiimoteEmu/Extension/BalanceBoard.cpp
new file mode 100644
index 0000000000..38a782f785
--- /dev/null
+++ b/Source/Core/Core/HW/WiimoteEmu/Extension/BalanceBoard.cpp
@@ -0,0 +1,109 @@
+// Copyright 2022 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Core/HW/WiimoteEmu/Extension/BalanceBoard.h"
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <cstring>
+
+#include "Common/BitUtils.h"
+#include "Common/Common.h"
+#include "Common/CommonTypes.h"
+#include "Common/MathUtil.h"
+#include "Common/Swap.h"
+
+#include "Core/HW/Wiimote.h"
+#include "Core/HW/WiimoteEmu/Extension/DesiredExtensionState.h"
+#include "Core/HW/WiimoteEmu/WiimoteEmu.h"
+
+#include "InputCommon/ControllerEmu/Control/Input.h"
+#include "InputCommon/ControllerEmu/ControlGroup/AnalogStick.h"
+#include "InputCommon/ControllerEmu/ControlGroup/Buttons.h"
+#include "InputCommon/ControllerEmu/ControlGroup/ControlGroup.h"
+#include "InputCommon/ControllerEmu/ControlGroup/Force.h"
+#include "InputCommon/ControllerEmu/ControlGroup/Tilt.h"
+
+namespace WiimoteEmu
+{
+constexpr std::array<u8, 6> balance_board_id{{0x00, 0x00, 0xa4, 0x20, 0x04, 0x02}};
+
+BalanceBoardExt::BalanceBoardExt() : Extension1stParty("BalanceBoard", _trans("Balance Board"))
+{
+}
+
+void BalanceBoardExt::BuildDesiredExtensionState(DesiredExtensionState* target_state)
+{
+  DataFormat bb_data = {};
+
+  bb_data.top_right = Common::swap16(0x0743);
+  bb_data.bottom_right = Common::swap16(0x11a2);
+  bb_data.top_left = Common::swap16(0x06a8);
+  bb_data.bottom_left = Common::swap16(0x4694);
+  bb_data.temperature = 0x19;
+  bb_data.battery = 0x83;
+
+  target_state->data = bb_data;
+}
+
+void BalanceBoardExt::Update(const DesiredExtensionState& target_state)
+{
+  DefaultExtensionUpdate<DataFormat>(&m_reg, target_state);
+}
+
+void BalanceBoardExt::Reset()
+{
+  EncryptedExtension::Reset();
+
+  m_reg.identifier = balance_board_id;
+
+  // Build calibration data:
+  m_reg.calibration = {{// Unused battery calibration
+                        0x01, 0x69, 0x00, 0x00,
+                        // Top right 0kg
+                        0x07, 0xbc,
+                        // Bottom right 0kg
+                        0x11, 0x8b,
+                        // Top left 0kg
+                        0x06, 0xba,
+                        // Bottom left 0kg
+                        0x46, 0x52,
+                        // Top right 17kg
+                        0x0e, 0x6e,
+                        // Bottom right 17kg
+                        0x18, 0x79}};
+  m_reg.calibration2 = {{// Top left 17kg
+                         0x0d, 0x5d,
+                         // Bottom left 17kg
+                         0x4d, 0x4c,
+                         // Top right 34kg
+                         0x15, 0x2e,
+                         // Bottom right 34kg
+                         0x1f, 0x71,
+                         // Top left 34kg
+                         0x14, 0x07,
+                         // Bottom left 34kg
+                         0x54, 0x51,
+                         // Checksum
+                         0xa9, 0x06, 0xb4, 0xf0}};
+  m_reg.calibration3 = {{0x19, 0x01}};
+
+  // UpdateCalibrationDataChecksum(m_reg.calibration, CALIBRATION_CHECKSUM_BYTES);
+}
+
+ControllerEmu::ControlGroup* BalanceBoardExt::GetGroup(BalanceBoardGroup group)
+{
+  return nullptr;
+}
+
+void BalanceBoardExt::DoState(PointerWrap& p)
+{
+  EncryptedExtension::DoState(p);
+}
+
+void BalanceBoardExt::LoadDefaults(const ControllerInterface& ciface)
+{
+}
+
+}  // namespace WiimoteEmu
diff --git a/Source/Core/Core/HW/WiimoteEmu/Extension/BalanceBoard.h b/Source/Core/Core/HW/WiimoteEmu/Extension/BalanceBoard.h
new file mode 100644
index 0000000000..db8e5a8bdb
--- /dev/null
+++ b/Source/Core/Core/HW/WiimoteEmu/Extension/BalanceBoard.h
@@ -0,0 +1,51 @@
+// Copyright 2022 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <array>
+
+#include "Core/HW/WiimoteCommon/WiimoteReport.h"
+#include "Core/HW/WiimoteEmu/Dynamics.h"
+#include "Core/HW/WiimoteEmu/Extension/Extension.h"
+
+namespace ControllerEmu
+{
+class ControlGroup;
+}  // namespace ControllerEmu
+
+namespace WiimoteEmu
+{
+enum class BalanceBoardGroup
+{
+};
+
+class BalanceBoardExt : public Extension1stParty
+{
+public:
+  struct DataFormat
+  {
+    u16 top_right;
+    u16 bottom_right;
+    u16 top_left;
+    u16 bottom_left;
+    u8 temperature;
+    u8 padding;
+    u8 battery;
+  };
+  static_assert(sizeof(DataFormat) == 12, "Wrong size");
+
+  BalanceBoardExt();
+
+  void BuildDesiredExtensionState(DesiredExtensionState* target_state) override;
+  void Update(const DesiredExtensionState& target_state) override;
+  void Reset() override;
+  void DoState(PointerWrap& p) override;
+
+  ControllerEmu::ControlGroup* GetGroup(BalanceBoardGroup group);
+
+  void LoadDefaults(const ControllerInterface& ciface) override;
+
+private:
+};
+}  // namespace WiimoteEmu
diff --git a/Source/Core/Core/HW/WiimoteEmu/Extension/DesiredExtensionState.h b/Source/Core/Core/HW/WiimoteEmu/Extension/DesiredExtensionState.h
index 4929c91cd1..4f52de1c9a 100644
--- a/Source/Core/Core/HW/WiimoteEmu/Extension/DesiredExtensionState.h
+++ b/Source/Core/Core/HW/WiimoteEmu/Extension/DesiredExtensionState.h
@@ -8,6 +8,7 @@
 
 #include "Common/BitUtils.h"
 
+#include "Core/HW/WiimoteEmu/Extension/BalanceBoard.h"
 #include "Core/HW/WiimoteEmu/Extension/Classic.h"
 #include "Core/HW/WiimoteEmu/Extension/DrawsomeTablet.h"
 #include "Core/HW/WiimoteEmu/Extension/Drums.h"
@@ -27,7 +28,8 @@ struct DesiredExtensionState
   using ExtensionData =
       std::variant<std::monostate, Nunchuk::DataFormat, Classic::DataFormat, Guitar::DataFormat,
                    Drums::DesiredState, Turntable::DataFormat, UDrawTablet::DataFormat,
-                   DrawsomeTablet::DataFormat, TaTaCon::DataFormat, Shinkansen::DesiredState>;
+                   DrawsomeTablet::DataFormat, TaTaCon::DataFormat, Shinkansen::DesiredState,
+                   BalanceBoardExt::DataFormat>;
   ExtensionData data = std::monostate();
 
   static_assert(std::is_same_v<std::monostate,
@@ -57,6 +59,9 @@ struct DesiredExtensionState
   static_assert(
       std::is_same_v<Shinkansen::DesiredState,
                      std::variant_alternative_t<ExtensionNumber::SHINKANSEN, ExtensionData>>);
+  static_assert(
+      std::is_same_v<BalanceBoardExt::DataFormat,
+                     std::variant_alternative_t<ExtensionNumber::BALANCE_BOARD, ExtensionData>>);
   static_assert(std::variant_size_v<DesiredExtensionState::ExtensionData> == ExtensionNumber::MAX);
 };
 
diff --git a/Source/Core/Core/HW/WiimoteEmu/Extension/Extension.h b/Source/Core/Core/HW/WiimoteEmu/Extension/Extension.h
index 4a055c597d..0431923384 100644
--- a/Source/Core/Core/HW/WiimoteEmu/Extension/Extension.h
+++ b/Source/Core/Core/HW/WiimoteEmu/Extension/Extension.h
@@ -85,11 +85,14 @@ public:
 
     // address 0x20
     std::array<u8, 0x10> calibration;
-    u8 unknown3[0x10];
+    std::array<u8, 0x10> calibration2;
 
     // address 0x40
     std::array<u8, 0x10> encryption_key_data;
-    u8 unknown4[0xA0];
+    u8 unknown3[0x10];
+    // Address 0x60
+    std::array<u8, 2> calibration3;
+    u8 unknown4[0x8e];
 
     // address 0xF0
     u8 encryption;
diff --git a/Source/Core/Core/HW/WiimoteEmu/ExtensionPort.h b/Source/Core/Core/HW/WiimoteEmu/ExtensionPort.h
index 86b1fd31f9..43b4aca6d1 100644
--- a/Source/Core/Core/HW/WiimoteEmu/ExtensionPort.h
+++ b/Source/Core/Core/HW/WiimoteEmu/ExtensionPort.h
@@ -23,6 +23,8 @@ enum ExtensionNumber : u8
   TATACON,
   SHINKANSEN,
 
+  BALANCE_BOARD,
+
   MAX
 };
 
diff --git a/Source/Core/Core/HW/WiimoteEmu/WiimoteEmu.cpp b/Source/Core/Core/HW/WiimoteEmu/WiimoteEmu.cpp
index a93ad379e8..501b5a5972 100644
--- a/Source/Core/Core/HW/WiimoteEmu/WiimoteEmu.cpp
+++ b/Source/Core/Core/HW/WiimoteEmu/WiimoteEmu.cpp
@@ -28,6 +28,7 @@
 #include "Core/HW/WiimoteCommon/WiimoteConstants.h"
 #include "Core/HW/WiimoteCommon/WiimoteHid.h"
 #include "Core/HW/WiimoteEmu/DesiredWiimoteState.h"
+#include "Core/HW/WiimoteEmu/Extension/BalanceBoard.h"
 #include "Core/HW/WiimoteEmu/Extension/Classic.h"
 #include "Core/HW/WiimoteEmu/Extension/DesiredExtensionState.h"
 #include "Core/HW/WiimoteEmu/Extension/DrawsomeTablet.h"
@@ -182,6 +183,7 @@ void Wiimote::Reset()
   {
     // Switch to desired M+ status and extension (if any).
     // M+ and EXT are reset on attachment.
+    // This also ensures that the balance board extension is attached if needed.
     HandleExtensionSwap(static_cast<ExtensionNumber>(m_attachments->GetSelectedAttachment()),
                         m_motion_plus_setting.GetValue());
   }
@@ -280,6 +282,7 @@ Wiimote::Wiimote(const unsigned int index) : m_index(index), m_bt_device_index(i
   m_attachments->AddAttachment(std::make_unique<WiimoteEmu::DrawsomeTablet>());
   m_attachments->AddAttachment(std::make_unique<WiimoteEmu::TaTaCon>());
   m_attachments->AddAttachment(std::make_unique<WiimoteEmu::Shinkansen>());
+  m_attachments->AddAttachment(std::make_unique<WiimoteEmu::BalanceBoardExt>());
 
   m_attachments->AddSetting(&m_motion_plus_setting, {_trans("Attach MotionPlus")}, true);
 
diff --git a/Source/Core/DolphinLib.props b/Source/Core/DolphinLib.props
index e41e9fc26a..f55b6aa43d 100644
--- a/Source/Core/DolphinLib.props
+++ b/Source/Core/DolphinLib.props
@@ -337,6 +337,7 @@
     <ClInclude Include="Core\HW\WiimoteEmu\Dynamics.h" />
     <ClInclude Include="Core\HW\WiimoteEmu\DesiredWiimoteState.h" />
     <ClInclude Include="Core\HW\WiimoteEmu\Encryption.h" />
+    <ClInclude Include="Core\HW\WiimoteEmu\Extension\BalanceBoard.h" />
     <ClInclude Include="Core\HW\WiimoteEmu\Extension\Classic.h" />
     <ClInclude Include="Core\HW\WiimoteEmu\Extension\DesiredExtensionState.h" />
     <ClInclude Include="Core\HW\WiimoteEmu\Extension\DrawsomeTablet.h" />
@@ -1001,6 +1002,7 @@
     <ClCompile Include="Core\HW\WiimoteEmu\Dynamics.cpp" />
     <ClCompile Include="Core\HW\WiimoteEmu\EmuSubroutines.cpp" />
     <ClCompile Include="Core\HW\WiimoteEmu\Encryption.cpp" />
+    <ClCompile Include="Core\HW\WiimoteEmu\Extension\BalanceBoard.cpp" />
     <ClCompile Include="Core\HW\WiimoteEmu\Extension\Classic.cpp" />
     <ClCompile Include="Core\HW\WiimoteEmu\Extension\DrawsomeTablet.cpp" />
     <ClCompile Include="Core\HW\WiimoteEmu\Extension\Drums.cpp" />