The Marlins selected Castano's contract from Triple-A Jacksonville on Sunday, Jordan McPherson of the Miami Herald reports.
Castano made an appearance for the Marlins in early April and was designated for assignment in June, but he'll rejoin the 26-man and 40-man rosters ahead of Sunday's series finale in Philadelphia. The 28-year-old could be a long-relief option Sunday behind opener Steven Okert, though Bryan Hoeing is also an option to cover bulk innings.