diff --git a/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp b/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp
--- a/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp
+++ b/mlir/lib/Dialect/Complex/IR/ComplexOps.cpp
@@ -150,6 +150,15 @@
     if (getRhs() == add.getRhs())
       return add.getLhs();
 
+  // complex.sub(a, complex.constant<0.0, 0.0>) -> a
+  if (auto constantOp = getRhs().getDefiningOp<ConstantOp>()) {
+    auto arrayAttr = constantOp.getValue();
+    if (arrayAttr[0].cast<FloatAttr>().getValue().isZero() &&
+        arrayAttr[1].cast<FloatAttr>().getValue().isZero()) {
+      return getLhs();
+    }
+  }
+
   return {};
 }
 
diff --git a/mlir/test/Dialect/Complex/canonicalize.mlir b/mlir/test/Dialect/Complex/canonicalize.mlir
--- a/mlir/test/Dialect/Complex/canonicalize.mlir
+++ b/mlir/test/Dialect/Complex/canonicalize.mlir
@@ -144,4 +144,14 @@
   %add = complex.add %complex1, %complex2 : complex<f32>
   %sub = complex.sub %add, %complex2 : complex<f32>
   return %sub : complex<f32>
+}
+
+// CHECK-LABEL: func @complex_sub_zero
+func.func @complex_sub_zero() -> complex<f32> {
+  %complex1 = complex.constant [1.0 : f32, 0.0 : f32] : complex<f32>
+  %complex2 = complex.constant [0.0 : f32, 0.0 : f32] : complex<f32>
+  // CHECK: %[[CPLX:.*]] = complex.constant [1.000000e+00 : f32, 0.000000e+00 : f32] : complex<f32>
+  // CHECK-NEXT: return %[[CPLX:.*]] : complex<f32>
+  %sub = complex.sub %complex1, %complex2 : complex<f32>
+  return %sub : complex<f32>
 }
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