Alonso was acquired by the Padres from the Braves on Tuesday in exchange for cash considerations, Dennis Lin of The Athletic reports.
Alonso was placed on the restricted list Monday.
Alonso was outrighted off of Atlanta's roster Thursday.
Alonso's contract was selected by the Braves on Saturday.
Alonso will be a part of the Braves' 60-man roster, Gabe Burns of The Atlanta Journal-Constitution reports.
Alonso signed a minor-league contract with the Braves on Tuesday, Ken Rosenthal of The Athletic reports.
Alonso went 1-for-4 with an RBI in Sunday's 11-4 loss to the Cardinals.
Alonso went 2-for-5 with a two-run home run in a 3-2 loss against the Reds on Sunday.
Alonso went 2-for-3 with a walk, two doubles and two runs scored in a 3-2 loss to the Nationals during the first game of Wednesday's doubleheader.
Alonso will have his contract selected from Triple-A Albuquerque prior to Tuesday's game against the Nationals, Nick Groke of The Athletic reports.