Iran Press/ America: The MLS club confirmed this on their official website on Sunday.
Messi only joined the club in June after his contract with Paris Saint-Germain expired.
The 36-year-old has contributed 11 goals and eight assists in his first 14 matches for the club, as he inspired them to their first trophy in the form of the inaugural Leagues Cup.
He was however not able to lift them to the MLS playoffs.
Messi follows in the footsteps of Gonzalo Higuain and Lewis Morgan, who have won the Miami award in the past.
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