diff --git a/core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java b/core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java
index ca6e357469d0..6e52d841e4ad 100644
--- a/core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java
+++ b/core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java
@@ -1045,7 +1045,10 @@ public List<SqlNode> toSql(Window.Group group, ImmutableList<RexLiteral> constan
         };
         RexCall aggCall = (RexCall) winAggCall.accept(replaceConstants);
         List<SqlNode> operands = toSql(null, aggCall.operands);
-        rexOvers.add(createOverCall(aggFunction, operands, sqlWindow, winAggCall.distinct));
+        final SqlCall overCall =
+            createOverCall(aggFunction, operands, sqlWindow,
+                winAggCall.distinct, winAggCall.ignoreNulls);
+        rexOvers.add(overCall);
       }
       return rexOvers;
     }
@@ -1092,15 +1095,16 @@ private SqlCall toSql(@Nullable RexProgram program, RexOver rexOver) {
               orderList, isRows, lowerBound, upperBound, allowPartial, exclude, POS);
 
       final List<SqlNode> nodeList = toSql(program, rexOver.getOperands());
-      return createOverCall(sqlAggregateFunction, nodeList, sqlWindow, rexOver.isDistinct());
+      return createOverCall(sqlAggregateFunction, nodeList, sqlWindow,
+          rexOver.isDistinct(), rexOver.ignoreNulls());
     }
 
     private static SqlCall createOverCall(SqlAggFunction op, List<SqlNode> operands,
-        SqlWindow window, boolean isDistinct) {
+        SqlWindow window, boolean isDistinct, boolean ignoreNulls) {
       if (op instanceof SqlSumEmptyIsZeroAggFunction) {
         // Rewrite "SUM0(x) OVER w" to "COALESCE(SUM(x) OVER w, 0)"
         final SqlCall node =
-            createOverCall(SqlStdOperatorTable.SUM, operands, window, isDistinct);
+            createOverCall(SqlStdOperatorTable.SUM, operands, window, isDistinct, ignoreNulls);
         return SqlStdOperatorTable.COALESCE.createCall(POS, node, ZERO);
       }
       SqlCall aggFunctionCall;
@@ -1110,6 +1114,10 @@ private static SqlCall createOverCall(SqlAggFunction op, List<SqlNode> operands,
       } else {
         aggFunctionCall = op.createCall(POS, operands);
       }
+      if (ignoreNulls) {
+        aggFunctionCall =
+            SqlStdOperatorTable.IGNORE_NULLS.createCall(null, POS, aggFunctionCall);
+      }
       return SqlStdOperatorTable.OVER.createCall(POS, aggFunctionCall,
           window);
     }
diff --git a/core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java b/core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java
index d855bb96c380..6eba6a16ccd1 100644
--- a/core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java
+++ b/core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java
@@ -4584,6 +4584,32 @@ private void checkLiteral2(String expression, String expected) {
     sql(query).ok(expected);
   }
 
+  /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-6569">[CALCITE-6569]
+   * RelToSqlConverter support IGNORE NULLS for window functions</a>. */
+  @Test void testIgnoreNullsWindow() {
+    final String query0 = "SELECT LEAD(\"employee_id\", 2) IGNORE NULLS "
+        + "OVER (ORDER BY \"hire_date\") FROM \"employee\"";
+    final String expected0 = "SELECT LEAD(\"employee_id\", 2) IGNORE NULLS OVER (ORDER BY "
+        + "\"hire_date\")\n"
+        + "FROM \"foodmart\".\"employee\"";
+    sql(query0).ok(expected0);
+
+    final String query1 = "SELECT "
+        + "LAG(\"employee_id\", 1) IGNORE NULLS OVER (ORDER BY \"hire_date\"),"
+        + "FIRST_VALUE(\"employee_id\") IGNORE NULLS OVER (ORDER BY \"hire_date\"),"
+        + "LAST_VALUE(\"employee_id\") IGNORE NULLS OVER (ORDER BY \"hire_date\")"
+        + "FROM \"employee\"";
+    final String expected1 = "SELECT "
+        + "LAG(\"employee_id\", 1) IGNORE NULLS OVER (ORDER BY \"hire_date\"), "
+        + "FIRST_VALUE(\"employee_id\") IGNORE NULLS OVER (ORDER BY \"hire_date\""
+        + " RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW), "
+        + "LAST_VALUE(\"employee_id\") IGNORE NULLS OVER (ORDER BY \"hire_date\""
+        + " RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)\n"
+        + "FROM \"foodmart\".\"employee\"";
+    sql(query1).ok(expected1);
+  }
+
   /** Test case for
    * <a href="https://issues.apache.org/jira/browse/CALCITE-3112">[CALCITE-3112]
    * Support Window in RelToSqlConverter</a>. */