On February 16, 2021, Morimando signed a minor league contract with the Miami Marlins organization. On May 22, Morimando was selected to the active roster. He was designated for assignment on May 26 after allowing 4 earned runs in of an inning. He was outrighted to the Triple-A Jacksonville Jumbo Shrimp on May 31. On July 9, Morimando was re-selected to the active roster. Morimando tossed 5.0 scoreless innings against the Atlanta Braves, notching five strikeouts and walking four, but was designated for assignment the next day. He was again outrighted to Jacksonville on July 13. On August 9, Morimando's contract was once again selected by the Marlins. On August 14, Morimando was designated for assignment by the Marlins again.
