Gnabry was forced to miss part of the mid-season training camp in Doha due to problems with his Achilles tendon, which he sustained at the start of the month.
However, Bayern confirmed that the 24 year-old winger completed the full 90 minutes of training, including a match.
The news comes a day after top scorer Robert Lewandowksi returned to team training, the striker having undergone surgery after the 2-0 win over Wolfsburg on 21 December.
Gnabry has scored six times in the Bundesliga this season and set up a further six goals. Only Thomas Muller (11) has provided more league assists for Bayern.
Hansi Flick's side faces Hertha knowing it could be seven points off the top of the table if league-leader RB Leipzig beats Union Berlin.