Gather all ingredients.
Whisk together orange-flavored gelatin and boiling water in a large, heatproof bowl until fully dissolved.
Drain mandarin oranges and set aside at room temperature; reserve ½ cup of the light syrup. Whisk the ½ cup syrup into gelatin mixture (discard remaining syrup, or reserve for another use). Chill gelatin mixture, uncovered, until cool to the touch, about 15 minutes.
Whisk instant pudding into cooled gelatin mixture until combined. Return bowl to refrigerator and chill until slightly thickened, about 10 minutes.
Gently fold in whipped topping until just combined.
Add mandarin oranges and marshmallows, and fold until evenly distributed. Cover and chill mixture until set and slightly thickened, about 3 hours.
Serve in chilled bowls; garnish with more marshmallows. This recipe was developed by Amanda Stanfield
