diff --git a/toolchain/check/eval.cpp b/toolchain/check/eval.cpp
index b9135185865a..f9b01d4f9738 100644
--- a/toolchain/check/eval.cpp
+++ b/toolchain/check/eval.cpp
@@ -1568,9 +1568,10 @@ static auto TryEvalInstInContext(EvalContext& eval_context,
           eval_context, inst, &SemIR::AssociatedEntityType::interface_type_id,
           &SemIR::AssociatedEntityType::entity_type_id);
     case SemIR::BoundMethod::Kind:
-      return RebuildIfFieldsAreConstant(
-          eval_context, inst, &SemIR::BoundMethod::type_id,
-          &SemIR::BoundMethod::object_id, &SemIR::BoundMethod::function_id);
+      return RebuildIfFieldsAreConstant(eval_context, inst,
+                                        &SemIR::BoundMethod::type_id,
+                                        &SemIR::BoundMethod::object_id,
+                                        &SemIR::BoundMethod::function_decl_id);
     case SemIR::ClassType::Kind:
       return RebuildIfFieldsAreConstant(eval_context, inst,
                                         &SemIR::ClassType::specific_id);
diff --git a/toolchain/check/import_ref.cpp b/toolchain/check/import_ref.cpp
index 2989376e594b..5a686d30dd42 100644
--- a/toolchain/check/import_ref.cpp
+++ b/toolchain/check/import_ref.cpp
@@ -1452,7 +1452,8 @@ static auto TryResolveTypedInst(ImportRefResolver& resolver,
   CARBON_CHECK(resolver.import_types().GetInstId(inst.type_id) ==
                SemIR::BoundMethodType::SingletonInstId);
   auto object_id = GetLocalConstantInstId(resolver, inst.object_id);
-  auto function_id = GetLocalConstantInstId(resolver, inst.function_id);
+  auto function_decl_id =
+      GetLocalConstantInstId(resolver, inst.function_decl_id);
 
   if (resolver.HasNewWork()) {
     return ResolveResult::Retry();
@@ -1462,7 +1463,7 @@ static auto TryResolveTypedInst(ImportRefResolver& resolver,
       resolver, {.type_id = resolver.local_context().GetSingletonType(
                      SemIR::BoundMethodType::SingletonInstId),
                  .object_id = object_id,
-                 .function_id = function_id});
+                 .function_decl_id = function_decl_id});
 }
 
 static auto TryResolveTypedInst(ImportRefResolver& resolver, SemIR::Call inst)
diff --git a/toolchain/check/member_access.cpp b/toolchain/check/member_access.cpp
index aee62581d6ed..70355d9a4c1f 100644
--- a/toolchain/check/member_access.cpp
+++ b/toolchain/check/member_access.cpp
@@ -380,7 +380,7 @@ static auto PerformInstanceBinding(Context& context, SemIR::LocId loc_id,
             loc_id, {.type_id = context.GetSingletonType(
                          SemIR::BoundMethodType::SingletonInstId),
                      .object_id = base_id,
-                     .function_id = member_id});
+                     .function_decl_id = member_id});
       }
       [[fallthrough]];
     }
diff --git a/toolchain/lower/constant.cpp b/toolchain/lower/constant.cpp
index fd5ea63baaaf..965a1d8b8255 100644
--- a/toolchain/lower/constant.cpp
+++ b/toolchain/lower/constant.cpp
@@ -167,7 +167,7 @@ static auto EmitAsConstant(ConstantContext& context, SemIR::BoundMethod inst)
     -> llvm::Constant* {
   // Propagate just the function; the object is separately provided to the
   // enclosing call as an implicit argument.
-  return context.GetConstant(inst.function_id);
+  return context.GetConstant(inst.function_decl_id);
 }
 
 static auto EmitAsConstant(ConstantContext& context,
diff --git a/toolchain/lower/handle.cpp b/toolchain/lower/handle.cpp
index 7ac2b72f488c..5a22f570903e 100644
--- a/toolchain/lower/handle.cpp
+++ b/toolchain/lower/handle.cpp
@@ -109,7 +109,7 @@ auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
                 SemIR::BoundMethod inst) -> void {
   // Propagate just the function; the object is separately provided to the
   // enclosing call as an implicit argument.
-  context.SetLocal(inst_id, context.GetValue(inst.function_id));
+  context.SetLocal(inst_id, context.GetValue(inst.function_decl_id));
 }
 
 auto HandleInst(FunctionContext& context, SemIR::InstId /*inst_id*/,
diff --git a/toolchain/sem_ir/function.cpp b/toolchain/sem_ir/function.cpp
index c305c817e946..bfdf51d31497 100644
--- a/toolchain/sem_ir/function.cpp
+++ b/toolchain/sem_ir/function.cpp
@@ -25,7 +25,7 @@ auto GetCalleeFunction(const File& sem_ir, InstId callee_id) -> CalleeFunction {
 
   if (auto bound_method = sem_ir.insts().TryGetAs<BoundMethod>(callee_id)) {
     result.self_id = bound_method->object_id;
-    callee_id = bound_method->function_id;
+    callee_id = bound_method->function_decl_id;
   }
 
   // Identify the function we're calling.
diff --git a/toolchain/sem_ir/inst_namer.cpp b/toolchain/sem_ir/inst_namer.cpp
index 86bea57299bb..76b0b62e3439 100644
--- a/toolchain/sem_ir/inst_namer.cpp
+++ b/toolchain/sem_ir/inst_namer.cpp
@@ -523,7 +523,7 @@ auto InstNamer::CollectNamesInBlock(ScopeId top_scope_id,
         continue;
       }
       case CARBON_KIND(BoundMethod inst): {
-        auto type_id = sem_ir_->insts().Get(inst.function_id).type_id();
+        auto type_id = sem_ir_->insts().Get(inst.function_decl_id).type_id();
         if (auto fn_ty = sem_ir_->types().TryGetAs<FunctionType>(type_id)) {
           add_inst_name_id(sem_ir_->functions().Get(fn_ty->function_id).name_id,
                            ".bound");
@@ -763,7 +763,7 @@ auto InstNamer::CollectNamesInBlock(ScopeId top_scope_id,
       case CARBON_KIND(SpecificFunction inst): {
         InstId callee_id = inst.callee_id;
         if (auto method = sem_ir_->insts().TryGetAs<BoundMethod>(callee_id)) {
-          callee_id = method->function_id;
+          callee_id = method->function_decl_id;
         }
         auto type_id = sem_ir_->insts().Get(callee_id).type_id();
         if (auto fn_ty = sem_ir_->types().TryGetAs<FunctionType>(type_id)) {
diff --git a/toolchain/sem_ir/typed_insts.h b/toolchain/sem_ir/typed_insts.h
index bf0668ee2f4f..0d6f67c66dcc 100644
--- a/toolchain/sem_ir/typed_insts.h
+++ b/toolchain/sem_ir/typed_insts.h
@@ -398,7 +398,7 @@ struct BoundMethod {
   // self` parameter.
   InstId object_id;
   // The function being bound, whose type_id is always a `FunctionType`.
-  InstId function_id;
+  InstId function_decl_id;
 };
 
 // The type of bound method values.