Despite having signed for Atlanta United 2, Castanheira was selected by FC Dallas in the fourth round (88th overall) of the 2019 MLS SuperDraft on January 14, 2019.[6] His MLS rights were traded to expansion side Inter Miami CF on January 8, 2020, in exchange for a fourth-round pick in the 2020 MLS SuperDraft.[7]
Following the 2021 season, Castanheira's contract option was declined by Miami.[10]
On December 17, 2021, Dylan was announced as a member of Atlanta United for the following season.[11] Castanheira's contract option was declined by Atlanta following the 2022 season.[12]