diff --git a/flang/lib/Lower/OpenMP/OpenMP.cpp b/flang/lib/Lower/OpenMP/OpenMP.cpp
index a89029b720e788..83bd18bc9fbe31 100644
--- a/flang/lib/Lower/OpenMP/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP/OpenMP.cpp
@@ -2073,7 +2073,9 @@ static void genStandaloneSimd(lower::AbstractConverter &converter,
                      loopNestClauseOps, iv);
 
   EntryBlockArgs simdArgs;
-  // TODO: Add private, reduction syms and vars.
+  // TODO: Add private syms and vars.
+  simdArgs.reduction.syms = simdReductionSyms;
+  simdArgs.reduction.vars = simdClauseOps.reductionVars;
   auto simdOp =
       genWrapperOp<mlir::omp::SimdOp>(converter, loc, simdClauseOps, simdArgs);
 
@@ -2231,7 +2233,9 @@ static void genCompositeDistributeParallelDoSimd(
   wsloopOp.setComposite(/*val=*/true);
 
   EntryBlockArgs simdArgs;
-  // TODO: Add private, reduction syms and vars.
+  // TODO: Add private syms and vars.
+  simdArgs.reduction.syms = simdReductionSyms;
+  simdArgs.reduction.vars = simdClauseOps.reductionVars;
   auto simdOp =
       genWrapperOp<mlir::omp::SimdOp>(converter, loc, simdClauseOps, simdArgs);
   simdOp.setComposite(/*val=*/true);
@@ -2288,7 +2292,9 @@ static void genCompositeDistributeSimd(lower::AbstractConverter &converter,
   distributeOp.setComposite(/*val=*/true);
 
   EntryBlockArgs simdArgs;
-  // TODO: Add private, reduction syms and vars.
+  // TODO: Add private syms and vars.
+  simdArgs.reduction.syms = simdReductionSyms;
+  simdArgs.reduction.vars = simdClauseOps.reductionVars;
   auto simdOp =
       genWrapperOp<mlir::omp::SimdOp>(converter, loc, simdClauseOps, simdArgs);
   simdOp.setComposite(/*val=*/true);
@@ -2345,7 +2351,9 @@ static void genCompositeDoSimd(lower::AbstractConverter &converter,
   wsloopOp.setComposite(/*val=*/true);
 
   EntryBlockArgs simdArgs;
-  // TODO: Add private, reduction syms and vars.
+  // TODO: Add private syms and vars.
+  simdArgs.reduction.syms = simdReductionSyms;
+  simdArgs.reduction.vars = simdClauseOps.reductionVars;
   auto simdOp =
       genWrapperOp<mlir::omp::SimdOp>(converter, loc, simdClauseOps, simdArgs);
   simdOp.setComposite(/*val=*/true);
diff --git a/flang/test/Lower/OpenMP/simd.f90 b/flang/test/Lower/OpenMP/simd.f90
index 3b2aeceb4c3f9f..520c78043283d7 100644
--- a/flang/test/Lower/OpenMP/simd.f90
+++ b/flang/test/Lower/OpenMP/simd.f90
@@ -4,6 +4,8 @@
 ! RUN: %flang_fc1 -flang-experimental-hlfir -emit-hlfir -fopenmp -fopenmp-version=50 %s -o - | FileCheck %s
 ! RUN: bbc -hlfir -emit-hlfir -fopenmp -fopenmp-version=50 %s -o - | FileCheck %s
 
+!CHECK: omp.declare_reduction @[[REDUCER:.*]] : i32
+
 !CHECK-LABEL: func @_QPsimd()
 subroutine simd
   integer :: i
@@ -274,3 +276,25 @@ subroutine lastprivate_with_simd
     sum = i + 1
   end do
 end subroutine
+
+!CHECK-LABEL: func @_QPsimd_with_reduction_clause()
+subroutine simd_with_reduction_clause
+  integer :: i, x
+  x = 0
+  ! CHECK: %[[LB:.*]] = arith.constant 1 : i32
+  ! CHECK-NEXT: %[[UB:.*]] = arith.constant 9 : i32
+  ! CHECK-NEXT: %[[STEP:.*]] = arith.constant 1 : i32
+  ! CHECK-NEXT: omp.simd reduction(@[[REDUCER]] %[[X:.*]]#0 -> %[[X_RED:.*]] : !fir.ref<i32>) {
+  ! CHECK-NEXT: omp.loop_nest (%[[I:.*]]) : i32 = (%[[LB]]) to (%[[UB]]) inclusive step (%[[STEP]]) {
+  !$omp simd reduction(+:x)
+  do i=1, 9
+    ! CHECK: %[[X_DECL:.*]]:2 = hlfir.declare %[[X_RED]] {uniq_name = "_QFsimd_with_reduction_clauseEx"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+    ! CHECK: fir.store %[[I]] to %[[LOCAL:.*]]#1 : !fir.ref<i32>
+    ! CHECK: %[[X_LD:.*]] = fir.load %[[X_DECL]]#0 : !fir.ref<i32>
+    ! CHECK: %[[I_LD:.*]] = fir.load %[[LOCAL]]#0 : !fir.ref<i32>
+    ! CHECK: %[[SUM:.*]] = arith.addi %[[X_LD]], %[[I_LD]] : i32
+    ! CHECK: hlfir.assign %[[SUM]] to %[[X_DECL]]#0 : i32, !fir.ref<i32>
+    x = x+i
+  end do
+  !$OMP end simd
+end subroutine
diff --git a/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp b/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
index f552221bbdcaf9..fb11cd5f258285 100644
--- a/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
+++ b/mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp
@@ -2016,14 +2016,16 @@ void SimdOp::build(OpBuilder &builder, OperationState &state,
                    const SimdOperands &clauses) {
   MLIRContext *ctx = builder.getContext();
   // TODO Store clauses in op: linearVars, linearStepVars, privateVars,
-  // privateSyms, reductionVars, reductionByref, reductionSyms.
+  // privateSyms.
   SimdOp::build(builder, state, clauses.alignedVars,
                 makeArrayAttr(ctx, clauses.alignments), clauses.ifExpr,
                 /*linear_vars=*/{}, /*linear_step_vars=*/{},
                 clauses.nontemporalVars, clauses.order, clauses.orderMod,
                 /*private_vars=*/{}, /*private_syms=*/nullptr,
-                /*reduction_vars=*/{}, /*reduction_byref=*/nullptr,
-                /*reduction_syms=*/nullptr, clauses.safelen, clauses.simdlen);
+                clauses.reductionVars,
+                makeDenseBoolArrayAttr(ctx, clauses.reductionByref),
+                makeArrayAttr(ctx, clauses.reductionSyms), clauses.safelen,
+                clauses.simdlen);
 }
 
 LogicalResult SimdOp::verify() {
diff --git a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
index 19d80fbbd699b0..3611ea4da318b5 100644
--- a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
@@ -1786,6 +1786,20 @@ convertOrderKind(std::optional<omp::ClauseOrderKind> o) {
   llvm_unreachable("Unknown ClauseOrderKind kind");
 }
 
+static LogicalResult simdOpSupported(omp::SimdOp op) {
+  if (!op.getLinearVars().empty() || !op.getLinearStepVars().empty())
+    return op.emitError("linear clause not yet supported");
+
+  if (!op.getPrivateVars().empty() || op.getPrivateSyms())
+    return op.emitError("privatization clauses not yet supported");
+
+  if (!op.getReductionVars().empty() || op.getReductionByref() ||
+      op.getReductionSyms())
+    return op.emitError("reduction clause not yet supported");
+
+  return success();
+}
+
 /// Converts an OpenMP simd loop into LLVM IR using OpenMPIRBuilder.
 static LogicalResult
 convertOmpSimd(Operation &opInst, llvm::IRBuilderBase &builder,
@@ -1793,11 +1807,8 @@ convertOmpSimd(Operation &opInst, llvm::IRBuilderBase &builder,
   auto simdOp = cast<omp::SimdOp>(opInst);
   auto loopOp = cast<omp::LoopNestOp>(simdOp.getWrappedLoop());
 
-  if (!simdOp.getLinearVars().empty() || !simdOp.getLinearStepVars().empty() ||
-      !simdOp.getPrivateVars().empty() || simdOp.getPrivateSyms() ||
-      !simdOp.getReductionVars().empty() || simdOp.getReductionByref() ||
-      simdOp.getReductionSyms())
-    return opInst.emitError("unhandled clauses for translation to LLVM IR");
+  if (failed(simdOpSupported(simdOp)))
+    return failure();
 
   llvm::OpenMPIRBuilder::LocationDescription ompLoc(builder);