diff --git a/datafusion/expr/src/logical_plan/invariants.rs b/datafusion/expr/src/logical_plan/invariants.rs
index f36653694c21..263573ad3865 100644
--- a/datafusion/expr/src/logical_plan/invariants.rs
+++ b/datafusion/expr/src/logical_plan/invariants.rs
@@ -362,11 +362,11 @@ fn check_aggregation_in_scalar_subquery(
     inner_plan: &LogicalPlan,
     agg: &Aggregate,
 ) -> Result<()> {
-    if agg.aggr_expr.is_empty() {
-        return plan_err!(
-            "Correlated scalar subquery must be aggregated to return at most one row"
-        );
-    }
+    // The grouping is what makes the subquery scalar, not the aggregation. An
+    // empty GROUP BY returns one row, and a GROUP BY on only correlated columns
+    // returns at most one row per set of outer values. So subqueries without
+    // aggregate expressions are allowed as long as the GROUP BY check below
+    // passes.
     if !agg.group_expr.is_empty() {
         let correlated_exprs = get_correlated_expressions(inner_plan)?;
         let inner_subquery_cols =
diff --git a/datafusion/sqllogictest/test_files/subquery.slt b/datafusion/sqllogictest/test_files/subquery.slt
index 2a022b947d0f..546eaffa58bb 100644
--- a/datafusion/sqllogictest/test_files/subquery.slt
+++ b/datafusion/sqllogictest/test_files/subquery.slt
@@ -446,9 +446,30 @@ SELECT t1_id, (SELECT t3_int FROM t3 WHERE t3.t3_id = t1.t1_id) as t3_int from t
 44 3
 
 
-#non_aggregated_correlated_scalar_subquery
-statement error DataFusion error: Invalid \(non-executable\) plan after Analyzer\ncaused by\nError during planning: Correlated scalar subquery must be aggregated to return at most one row
+# A GROUP BY on only correlated columns returns at most one row per outer row,
+# so no aggregate function is needed to make the subquery scalar.
+#grouped_correlated_scalar_subquery_without_aggregate
+query II rowsort
 SELECT t1_id, (SELECT t2_int FROM t2 WHERE t2.t2_int = t1_int group by t2_int) as t2_int from t1
+----
+11 1
+22 NULL
+33 3
+44 NULL
+
+query TT
+explain SELECT t1_id, (SELECT t2_int FROM t2 WHERE t2.t2_int = t1_int group by t2_int) as t2_int from t1
+----
+logical_plan
+01)Projection: t1.t1_id, __scalar_sq_1.t2_int AS t2_int
+02)--Left Join: t1.t1_int = __scalar_sq_1.t2_int
+03)----TableScan: t1 projection=[t1_id, t1_int]
+04)----SubqueryAlias: __scalar_sq_1
+05)------Aggregate: groupBy=[[t2.t2_int]], aggr=[[]]
+06)--------TableScan: t2 projection=[t2_int]
+
+# A GROUP BY on a non-correlated column is still rejected, see
+# `aggregated_correlated_scalar_subquery_with_extra_group_by_columns` below.
 
 #non_aggregated_correlated_scalar_subquery_with_limit
 statement error DataFusion error: Invalid \(non-executable\) plan after Analyzer\ncaused by\nError during planning: Correlated scalar subquery must be aggregated to return at most one row