diff --git a/velox/functions/prestosql/tests/JsonCastTest.cpp b/velox/functions/prestosql/tests/JsonCastTest.cpp
index 95943d7286cc..cbfa04886737 100644
--- a/velox/functions/prestosql/tests/JsonCastTest.cpp
+++ b/velox/functions/prestosql/tests/JsonCastTest.cpp
@@ -1033,6 +1033,52 @@ TEST_F(JsonCastTest, orderOfKeys) {
   testCast(data, map);
 }
 
+TEST_F(JsonCastTest, toRowOfArray) {
+  auto data = makeFlatVector<std::string>(
+      {
+          R"({"c0": [1, 2, 3], "c1": 1.2})",
+          R"({"c0": [], "c1": 1.3})",
+          R"({"c0": [10, null, 20, null], "c1": 1.4})",
+      },
+      JSON());
+
+  auto expected = makeRowVector({
+      makeArrayVectorFromJson<int64_t>({
+          "[1, 2, 3]",
+          "[]",
+          "[10, null, 20, null]",
+      }),
+  });
+
+  testCast(data, expected);
+}
+
+TEST_F(JsonCastTest, toRowDuplicateKey) {
+  std::vector<std::optional<std::string>> jsonStrings = {
+      R"({"c0": 1, "c1": 1.1})",
+      R"({"c0": 2, "c1": 1.2, "C0": 45})", // Duplicate keys: c0, C0.
+      R"({"c0": 3, "c1": 1.3, "c0": 55})", // Duplicate keys: c0, c0.
+      R"({"c0": 4, "c1": 1.4, "c2": 65})",
+  };
+
+  testThrow<std::string>(
+      JSON(),
+      ROW({"c0", "c1"}, {INTEGER(), REAL()}),
+      jsonStrings,
+      "Duplicate field: c0");
+
+  auto data = makeNullableFlatVector<std::string>(jsonStrings, JSON());
+
+  auto expected = makeRowVector({
+      makeFlatVector<int32_t>({1, 0, 0, 4}),
+      makeFlatVector<float>({1.1, 0.0, 0.0, 1.4}),
+  });
+  expected->setNull(1, true);
+  expected->setNull(2, true);
+
+  testCast(data, expected, true /*try_cast*/);
+}
+
 TEST_F(JsonCastTest, toRow) {
   // Test casting to ROW from JSON arrays.
   auto array = makeNullableFlatVector<JsonNativeType>(
@@ -1053,7 +1099,7 @@ TEST_F(JsonCastTest, toRow) {
   auto map = makeNullableFlatVector<JsonNativeType>(
       {R"({"c0":123,"c1":"abc","c2":true})"_sv,
        R"({"c1":"abc","c2":true,"c0":123})"_sv,
-       R"({"c0":123,"c2":true,"c0":456})"_sv,
+       R"({"c10":123,"c2":true,"c0":456})"_sv,
        R"({"c3":123,"c4":"abc","c2":false})"_sv,
        R"({"c0":null,"c2":false})"_sv,
        R"({"c0":null,"c2":null,"c1":null})"_sv},
@@ -1074,17 +1120,17 @@ TEST_F(JsonCastTest, toRow) {
 
   // Use a mix of lower case and upper case JSON keys.
   map = makeNullableFlatVector<JsonNativeType>(
-      {R"({"c0":123,"c1":"abc","c2":true})"_sv,
-       R"({"c1":"abc","c2":true,"c0":123})"_sv,
-       R"({"c0":123,"c2":true,"c0":456})"_sv,
-       R"({"c3":123,"c4":"abc","c2":false})"_sv,
+      {R"({"C0":123,"C1":"abc","C2":true})"_sv,
+       R"({"c1":"abc","C2":true,"c0":123})"_sv,
+       R"({"C10":123,"C2":true,"c0":456})"_sv,
+       R"({"c3":123,"C4":"abc","c2":false})"_sv,
        R"({"c0":null,"c2":false})"_sv,
-       R"({"c0":null,"c2":null,"c1":null})"_sv},
+       R"({"c0":null,"c2":null,"C1":null})"_sv},
       JSON());
   testCast(map, makeRowVector({child4, child5, child6}));
 
   // Use a mix of lower case and upper case field names in target ROW type.
-  testCast(map, makeRowVector({child4, child5, child6}));
+  testCast(map, makeRowVector({"c0", "C1", "C2"}, {child4, child5, child6}));
 
   // Test casting to ROW from JSON null.
   auto null = makeNullableFlatVector<JsonNativeType>({"null"_sv}, JSON());
diff --git a/velox/functions/prestosql/types/JsonType.cpp b/velox/functions/prestosql/types/JsonType.cpp
index 4f90f5200866..07c629e7f052 100644
--- a/velox/functions/prestosql/types/JsonType.cpp
+++ b/velox/functions/prestosql/types/JsonType.cpp
@@ -856,30 +856,44 @@ struct CastFromJsonTypedImpl {
         }
       } else {
         SIMDJSON_ASSIGN_OR_RAISE(auto object, value.get_object());
-        folly::F14FastMap<std::string, simdjson::ondemand::value> lowerCaseKeys(
-            object.count_fields());
+
+        // TODO Populate this mapping once, not per-row.
+        // Mapping from lower-case field names of the target RowType to their
+        // indices.
+        folly::F14FastMap<std::string, int32_t> fieldIndices;
+        const auto size = rowType.size();
+        for (auto i = 0; i < size; ++i) {
+          auto key = rowType.nameOf(i);
+          boost::algorithm::to_lower(key);
+          fieldIndices[key] = i;
+        }
+
         std::string key;
         for (auto fieldResult : object) {
           SIMDJSON_ASSIGN_OR_RAISE(auto field, fieldResult);
           if (!field.value().is_null()) {
             SIMDJSON_ASSIGN_OR_RAISE(key, field.unescaped_key(true));
             boost::algorithm::to_lower(key);
-            lowerCaseKeys[key] = field.value();
+
+            auto it = fieldIndices.find(key);
+            if (it != fieldIndices.end()) {
+              const auto index = it->second;
+
+              VELOX_USER_CHECK_GE(index, 0, "Duplicate field: {}", key);
+              it->second = -1;
+
+              SIMDJSON_TRY(VELOX_DYNAMIC_TYPE_DISPATCH(
+                  CastFromJsonTypedImpl<simdjson::ondemand::value>::apply,
+                  rowType.childAt(index)->kind(),
+                  field.value(),
+                  writerTyped.get_writer_at(index)));
+            }
           }
         }
-        for (column_index_t numFields = rowType.size(), i = 0; i < numFields;
-             ++i) {
-          key = rowType.nameOf(i);
-          boost::algorithm::to_lower(key);
-          auto it = lowerCaseKeys.find(key);
-          if (it == lowerCaseKeys.end()) {
-            writerTyped.set_null_at(i);
-          } else {
-            SIMDJSON_TRY(VELOX_DYNAMIC_TYPE_DISPATCH(
-                CastFromJsonTypedImpl<simdjson::ondemand::value>::apply,
-                rowType.childAt(i)->kind(),
-                it->second,
-                writerTyped.get_writer_at(i)));
+
+        for (const auto& [key, index] : fieldIndices) {
+          if (index >= 0) {
+            writerTyped.set_null_at(index);
           }
         }
       }
@@ -1038,7 +1052,7 @@ class JsonCastOperator : public exec::CastOperator {
       maxSize = std::max(maxSize, input.size());
     });
     paddedInput_.resize(maxSize + simdjson::SIMDJSON_PADDING);
-    rows.applyToSelected([&](auto row) {
+    context.applyToSelectedNoThrow(rows, [&](auto row) {
       writer.setOffset(row);
       if (inputVector->isNullAt(row)) {
         writer.commitNull();