The 22-year-old racked up four goals and two assists during the month as the Cityzens posted a 2W-1L-2D league record.
Castellanos' goals proved significant in delivering results, as he recorded braces to account for all of NYCFC's scoring in wins against Inter Miami CF on August 14 and the Supporters' Shield-leading New England Revolution on August 28. Those were the fifth and sixth multi-goal performances of Castellanos' MLS career.
This marks the second time that Castellanos has received Player of the Month honors, having previously taken home the award in September/October 2020.
The Argentine is enjoying another productive all-around season for NYCFC, with 11 goals and six assists across 21 games. He's one assist shy of matching the output from his career-best MLS season of 2019, when he tallied 11g/7a in 30 games.