Drain pineapple, reserving juices; set pineapple aside. In a small saucepan, combine cornstarch and pineapple juice until smooth. Bring to a boil; cook and stir for 2 minutes or until thickened. Cover and refrigerate until cool.
In a large serving bowl, combine the honeydew, oranges, mint and reserved pineapple. Stir in pineapple juice mixture. Cover and refrigerate until serving.