diff --git a/src/main/java/com/kintone/client/KintoneApi.java b/src/main/java/com/kintone/client/KintoneApi.java
index 3298dacb..8fe494b8 100644
--- a/src/main/java/com/kintone/client/KintoneApi.java
+++ b/src/main/java/com/kintone/client/KintoneApi.java
@@ -85,6 +85,7 @@
 import com.kintone.client.api.record.UpdateRecordStatusResponseBody;
 import com.kintone.client.api.record.UpdateRecordStatusesResponseBody;
 import com.kintone.client.api.record.UpdateRecordsResponseBody;
+import com.kintone.client.api.record.UpsertRecordsResponseBody;
 import com.kintone.client.api.schema.GetApiListResponseBody;
 import com.kintone.client.api.space.AddGuestsResponseBody;
 import com.kintone.client.api.space.AddSpaceFromTemplateResponseBody;
@@ -112,6 +113,7 @@ public enum KintoneApi {
     GET_RECORDS(GET, "records", GetRecordsResponseBody.class),
     ADD_RECORDS(POST, "records", AddRecordsResponseBody.class),
     UPDATE_RECORDS(PUT, "records", UpdateRecordsResponseBody.class),
+    UPSERT_RECORDS(PUT, "records", UpsertRecordsResponseBody.class),
     DELETE_RECORDS(DELETE, "records", DeleteRecordsResponseBody.class),
     CREATE_CURSOR(POST, "records/cursor", CreateCursorResponseBody.class),
     GET_RECORDS_BY_CURSOR(GET, "records/cursor", GetRecordsByCursorResponseBody.class),
diff --git a/src/main/java/com/kintone/client/RecordClient.java b/src/main/java/com/kintone/client/RecordClient.java
index d568d9c2..8bebad7e 100644
--- a/src/main/java/com/kintone/client/RecordClient.java
+++ b/src/main/java/com/kintone/client/RecordClient.java
@@ -32,12 +32,15 @@
 import com.kintone.client.api.record.UpdateRecordStatusesResponseBody;
 import com.kintone.client.api.record.UpdateRecordsRequest;
 import com.kintone.client.api.record.UpdateRecordsResponseBody;
+import com.kintone.client.api.record.UpsertRecordsRequest;
+import com.kintone.client.api.record.UpsertRecordsResponseBody;
 import com.kintone.client.model.Order;
 import com.kintone.client.model.record.PostedRecordComment;
 import com.kintone.client.model.record.Record;
 import com.kintone.client.model.record.RecordComment;
 import com.kintone.client.model.record.RecordForUpdate;
 import com.kintone.client.model.record.RecordRevision;
+import com.kintone.client.model.record.RecordUpsertResult;
 import com.kintone.client.model.record.StatusAction;
 import com.kintone.client.model.record.UpdateKey;
 import java.util.List;
@@ -535,6 +538,32 @@ public UpdateRecordsResponseBody updateRecords(UpdateRecordsRequest request) {
         return client.call(KintoneApi.UPDATE_RECORDS, request, handlers);
     }
 
+    /**
+     * Inserts or updates details of multiple records in an App, by specifying their record numbers,
+     * or their unique keys. If the record exists, it will be updated. If it does not exist, a new
+     * record will be created.
+     *
+     * @param app the App ID
+     * @param records a list of objects that include id/updateKey, revision and record objects
+     * @return a list of record update results. See {@link RecordUpsertResult}
+     */
+    public List<RecordUpsertResult> upsertRecords(long app, List<RecordForUpdate> records) {
+        UpsertRecordsRequest req = new UpsertRecordsRequest();
+        req.setApp(app);
+        req.setRecords(records);
+        return upsertRecords(req).getRecords();
+    }
+
+    /**
+     * Inserts or updates details of multiple records in an App.
+     *
+     * @param request the request parameters. See {@link UpsertRecordsRequest}
+     * @return the response data. See {@link UpsertRecordsResponseBody}
+     */
+    public UpsertRecordsResponseBody upsertRecords(UpsertRecordsRequest request) {
+        return client.call(KintoneApi.UPSERT_RECORDS, request, handlers);
+    }
+
     /**
      * Updates the Status of a record of an App, that was set with the Process Management feature.
      *
diff --git a/src/main/java/com/kintone/client/api/record/UpsertRecordsRequest.java b/src/main/java/com/kintone/client/api/record/UpsertRecordsRequest.java
new file mode 100644
index 00000000..0a42691f
--- /dev/null
+++ b/src/main/java/com/kintone/client/api/record/UpsertRecordsRequest.java
@@ -0,0 +1,23 @@
+package com.kintone.client.api.record;
+
+import com.kintone.client.api.KintoneRequest;
+import com.kintone.client.model.record.RecordForUpdate;
+import java.util.List;
+import lombok.Data;
+
+/** A request object for Upsert Records API. */
+@Data
+public class UpsertRecordsRequest implements KintoneRequest {
+
+    /** The App ID (required). */
+    private Long app;
+
+    /** A list of objects that include id/updateKey, revision and record objects (required). */
+    private List<RecordForUpdate> records;
+
+    /**
+     * If set to true, the UPSERT mode will be enabled. In UPSERT mode, if the specified record
+     * exists, it will be updated. If it does not exist, a new record will be created (optional).
+     */
+    private final Boolean upsert = true;
+}
diff --git a/src/main/java/com/kintone/client/api/record/UpsertRecordsResponseBody.java b/src/main/java/com/kintone/client/api/record/UpsertRecordsResponseBody.java
new file mode 100644
index 00000000..8a1ac313
--- /dev/null
+++ b/src/main/java/com/kintone/client/api/record/UpsertRecordsResponseBody.java
@@ -0,0 +1,14 @@
+package com.kintone.client.api.record;
+
+import com.kintone.client.api.KintoneResponseBody;
+import com.kintone.client.model.record.RecordUpsertResult;
+import java.util.List;
+import lombok.Value;
+
+/** A response object for Upsert Records API. */
+@Value
+public class UpsertRecordsResponseBody implements KintoneResponseBody {
+
+    /** A list of objects that include the record IDs, updated revisions, and operations. */
+    private final List<RecordUpsertResult> records;
+}
diff --git a/src/main/java/com/kintone/client/model/record/RecordOperationType.java b/src/main/java/com/kintone/client/model/record/RecordOperationType.java
new file mode 100644
index 00000000..a86ea25d
--- /dev/null
+++ b/src/main/java/com/kintone/client/model/record/RecordOperationType.java
@@ -0,0 +1,10 @@
+package com.kintone.client.model.record;
+
+/** The type of operation performed on a record when using UPSERT mode in Update Records API. */
+public enum RecordOperationType {
+    /** An existing record was updated. */
+    UPDATE,
+
+    /** A new record was created. */
+    INSERT
+}
diff --git a/src/main/java/com/kintone/client/model/record/RecordUpsertResult.java b/src/main/java/com/kintone/client/model/record/RecordUpsertResult.java
new file mode 100644
index 00000000..fd848ff4
--- /dev/null
+++ b/src/main/java/com/kintone/client/model/record/RecordUpsertResult.java
@@ -0,0 +1,20 @@
+package com.kintone.client.model.record;
+
+import lombok.Value;
+
+/** A value that contains the record ID, revision, and operation, returned by Upsert Records API. */
+@Value
+public class RecordUpsertResult {
+
+    /** The Record ID */
+    private final long id;
+
+    /** The revision number of the record after updating or creating the record. */
+    private final long revision;
+
+    /**
+     * The operation that was performed. UPDATE (existing record was updated) or INSERT (new record
+     * was created). Null when not using UPSERT mode.
+     */
+    private final RecordOperationType operation;
+}
diff --git a/src/test/java/com/kintone/client/RecordClientTest.java b/src/test/java/com/kintone/client/RecordClientTest.java
index 94fc8ec1..d46b6f9e 100644
--- a/src/test/java/com/kintone/client/RecordClientTest.java
+++ b/src/test/java/com/kintone/client/RecordClientTest.java
@@ -35,11 +35,15 @@
 import com.kintone.client.api.record.UpdateRecordStatusesResponseBody;
 import com.kintone.client.api.record.UpdateRecordsRequest;
 import com.kintone.client.api.record.UpdateRecordsResponseBody;
+import com.kintone.client.api.record.UpsertRecordsRequest;
+import com.kintone.client.api.record.UpsertRecordsResponseBody;
 import com.kintone.client.model.Order;
 import com.kintone.client.model.record.Record;
 import com.kintone.client.model.record.RecordComment;
 import com.kintone.client.model.record.RecordForUpdate;
+import com.kintone.client.model.record.RecordOperationType;
 import com.kintone.client.model.record.RecordRevision;
+import com.kintone.client.model.record.RecordUpsertResult;
 import com.kintone.client.model.record.StatusAction;
 import com.kintone.client.model.record.UpdateKey;
 import java.util.Arrays;
@@ -548,6 +552,40 @@ public void updateRecords_UpdateRecordsRequest() {
         assertThat(mockClient.getLastBody()).isEqualTo(req);
     }
 
+    @Test
+    public void upsertRecords_long_List() {
+        RecordForUpdate up1 = new RecordForUpdate(1L, new Record());
+        RecordForUpdate up2 = new RecordForUpdate(new UpdateKey("text", "test"), new Record());
+        RecordUpsertResult result1 = new RecordUpsertResult(1, 2, RecordOperationType.UPDATE);
+        RecordUpsertResult result2 = new RecordUpsertResult(100, 2, RecordOperationType.INSERT);
+        mockClient.setResponseBody(new UpsertRecordsResponseBody(Arrays.asList(result1, result2)));
+
+        List<RecordForUpdate> records = Arrays.asList(up1, up2);
+        List<RecordUpsertResult> result = sut.upsertRecords(1, records);
+        assertThat(result).hasSize(2);
+        assertThat(result.get(0).getId()).isEqualTo(1);
+        assertThat(result.get(0).getRevision()).isEqualTo(2);
+        assertThat(result.get(0).getOperation()).isEqualTo(RecordOperationType.UPDATE);
+        assertThat(result.get(1).getId()).isEqualTo(100);
+        assertThat(result.get(1).getRevision()).isEqualTo(2);
+        assertThat(result.get(1).getOperation()).isEqualTo(RecordOperationType.INSERT);
+        assertThat(mockClient.getLastApi()).isEqualTo(KintoneApi.UPSERT_RECORDS);
+        assertThat(mockClient.getLastBody()).isInstanceOf(UpsertRecordsRequest.class);
+        UpsertRecordsRequest expected = new UpsertRecordsRequest().setApp(1L).setRecords(records);
+        assertThat(mockClient.getLastBody()).usingRecursiveComparison().isEqualTo(expected);
+    }
+
+    @Test
+    public void upsertRecords_UpsertRecordsRequest() {
+        UpsertRecordsRequest req = new UpsertRecordsRequest();
+        UpsertRecordsResponseBody resp = new UpsertRecordsResponseBody(Collections.emptyList());
+        mockClient.setResponseBody(resp);
+
+        assertThat(sut.upsertRecords(req)).isEqualTo(resp);
+        assertThat(mockClient.getLastApi()).isEqualTo(KintoneApi.UPSERT_RECORDS);
+        assertThat(mockClient.getLastBody()).isEqualTo(req);
+    }
+
     @Test
     public void updateRecordStatus_long_long_String() {
         mockClient.setResponseBody(new UpdateRecordStatusResponseBody(10L));