diff --git a/workflow/controller/operator.go b/workflow/controller/operator.go
index d18ce328ab9a..96cab8df89a3 100644
--- a/workflow/controller/operator.go
+++ b/workflow/controller/operator.go
@@ -3285,44 +3285,66 @@ func (woc *wfOperationCtx) processAggregateNodeOutputs(scope *wfScope, prefix st
 	// Adding per-output aggregated value placeholders
 	for outputName, valueList := range outputParamValueLists {
 		key = fmt.Sprintf("%s.outputs.parameters.%s", prefix, outputName)
-		unmarshalSuccess := true
-		var unmarshalledList []interface{}
-		for _, value := range valueList {
-			// Only try to unmarshal things that look like json lists or dicts
-			// and especially avoid unstringified numbers which are valid JSON
-			valueTrim := strings.Trim(value, " ")
-			valueTrimLen := len(valueTrim)
-			if valueTrimLen > 0 &&
-				!((valueTrim[0] == '{' && valueTrim[valueTrimLen-1] == '}') ||
-					(valueTrim[0] == '[' && valueTrim[valueTrimLen-1] == ']')) {
-				unmarshalSuccess = false
-				break // This isn't a json list or dict, leave it
-			}
-			var unmarshalledValue interface{}
-			err := json.Unmarshal([]byte(value), &unmarshalledValue)
-			if err != nil {
-				unmarshalSuccess = false
-				break // Unmarshal failed, fall back to strings
-			}
-			unmarshalledList = append(unmarshalledList, unmarshalledValue)
-		}
-		var valueListJSON []byte
-		if unmarshalSuccess {
-			valueListJSON, err = json.Marshal(unmarshalledList)
-			if err != nil {
-				return err
-			}
-		} else {
-			valueListJSON, err = json.Marshal(valueList)
-			if err != nil {
-				return err
-			}
+		valueListJson, err := aggregatedJsonValueList(valueList)
+		if err != nil {
+			return err
 		}
-		scope.addParamToScope(key, string(valueListJSON))
+		scope.addParamToScope(key, valueListJson)
 	}
 	return nil
 }
 
+// tryJsonUnmarshal unmarshals each item in the list assuming it is
+// JSON and NOT a plain JSON value.
+// If returns success only if all items can be unmarshalled and are either
+// maps or lists
+func tryJsonUnmarshal(valueList []string) ([]interface{}, bool) {
+	success := true
+	var list []interface{}
+	for _, value := range valueList {
+		var unmarshalledValue interface{}
+		err := json.Unmarshal([]byte(value), &unmarshalledValue)
+		if err != nil {
+			success = false
+			break // Unmarshal failed, fall back to strings
+		}
+		switch unmarshalledValue.(type) {
+		case []interface{}:
+		case map[string]interface{}:
+			// Keep these types
+		default:
+			// Drop anything else
+			success = false
+		}
+		if !success {
+			break
+		}
+		list = append(list, unmarshalledValue)
+	}
+	return list, success
+}
+
+// aggregatedJsonValueList returns a string containing a JSON list, holding
+// all of the values from the valueList.
+// It tries to understand what's wanted from  inner JSON using tryJsonUnmarshall
+func aggregatedJsonValueList(valueList []string) (string, error) {
+	unmarshalledList, success := tryJsonUnmarshal(valueList)
+	var valueListJSON []byte
+	var err error
+	if success {
+		valueListJSON, err = json.Marshal(unmarshalledList)
+		if err != nil {
+			return "", err
+		}
+	} else {
+		valueListJSON, err = json.Marshal(valueList)
+		if err != nil {
+			return "", err
+		}
+	}
+	return string(valueListJSON), nil
+}
+
 // addParamToGlobalScope exports any desired node outputs to the global scope, and adds it to the global outputs.
 func (woc *wfOperationCtx) addParamToGlobalScope(param wfv1.Parameter) {
 	if param.GlobalName == "" {
diff --git a/workflow/controller/operator_aggregation_test.go b/workflow/controller/operator_aggregation_test.go
new file mode 100644
index 000000000000..b966c448a6d3
--- /dev/null
+++ b/workflow/controller/operator_aggregation_test.go
@@ -0,0 +1,64 @@
+package controller
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTryJsonUnmarshal(t *testing.T) {
+	for _, testcase := range []struct {
+		input    []string
+		success  bool
+		expected []interface{}
+	}{
+		{[]string{"1"}, false, nil},
+		{[]string{"1", "2"}, false, nil},
+		{[]string{"foo"}, false, nil},
+		{[]string{"foo", "bar"}, false, nil},
+		{[]string{`["1"]`, "2"}, false, nil},       // Fails on second element
+		{[]string{`{"foo":"1"}`, "2"}, false, nil}, // Fails on second element
+		{[]string{`["1"]`, `["2"]`}, true, []interface{}{[]interface{}{"1"}, []interface{}{"2"}}},
+		{[]string{`["1"]`, `["2"]`}, true, []interface{}{[]interface{}{"1"}, []interface{}{"2"}}},
+		{[]string{"\n[\"1\"]  \n", "\t[\"2\"]\t"}, true, []interface{}{[]interface{}{"1"}, []interface{}{"2"}}},
+		{[]string{`{"number":"1"}`, `{"number":"2"}`}, true, []interface{}{map[string]interface{}{"number": "1"}, map[string]interface{}{"number": "2"}}},
+		{[]string{`[{"foo":"apple", "bar":"pear"}]`, `{"foo":"banana"}`}, true, []interface{}{[]interface{}{map[string]interface{}{"bar": "pear", "foo": "apple"}}, map[string]interface{}{"foo": "banana"}}},
+	} {
+		t.Run(fmt.Sprintf("Unmarshal %v", testcase.input),
+			func(t *testing.T) {
+				list, success := tryJsonUnmarshal(testcase.input)
+				require.Equal(t, testcase.success, success)
+				if success {
+					assert.Equal(t, testcase.expected, list)
+				}
+			})
+	}
+}
+
+func TestAggregatedJsonValueList(t *testing.T) {
+	for _, testcase := range []struct {
+		input    []string
+		expected string
+	}{
+		{[]string{"1"}, `["1"]`},
+		{[]string{"1", "2"}, `["1","2"]`},
+		{[]string{"foo"}, `["foo"]`},
+		{[]string{"foo", "bar"}, `["foo","bar"]`},
+		{[]string{`["1"]`, "2"}, `["[\"1\"]","2"]`},               // This is expected, but not really useful
+		{[]string{`{"foo":"1"}`, "2"}, `["{\"foo\":\"1\"}","2"]`}, // This is expected, but not really useful
+		{[]string{`["1"]`, `["2"]`}, `[["1"],["2"]]`},
+		{[]string{` ["1"]`, `["2"] `}, `[["1"],["2"]]`},
+		{[]string{"\n[\"1\"]  \n", "\t[\"2\"]\t"}, `[["1"],["2"]]`},
+		{[]string{`{"number":"1"}`, `{"number":"2"}`}, `[{"number":"1"},{"number":"2"}]`},
+		{[]string{`[{"foo":"apple", "bar":"pear"}]`}, `[[{"bar":"pear","foo":"apple"}]]`}, // Sorted map keys here may make this a fragile test, can be dropped
+	} {
+		t.Run(fmt.Sprintf("Aggregate %v", testcase.input),
+			func(t *testing.T) {
+				result, err := aggregatedJsonValueList(testcase.input)
+				require.NoError(t, err)
+				assert.Equal(t, testcase.expected, result)
+			})
+	}
+}