Greece coach Fernando Santos called up Gekas after the 31-year-old forward publicly apologized last weekend for quitting the national team a year ago, citing animosity with teammates.
Charisteas, another 31-year-old Bundesliga veteran, was recalled despite his move back to lowly Greek club Panaitolikos.
Greece is hoping to regain its Group F lead from Croatia when the two meet in Athens on Oct. 7, before traveling to Georgia four days later. The Greeks are currently a point behind Croatia, which has 19 points from eight matches.
Goalkeepers: Alexandros Tzorvas (Palermo), Dionisis Chiotis (APOEL)
Defenders: Vassilis Torosidis (Olympiakos), Nikos Spyropoulos (Panathinaikos), Yiannis Zaradoukas (Olympiakos), Sokratis Papastathopoulos (Werder Bremen), Kyriakos Papadopoulos (Schalke), Avraam Papadopoulos (Olympiakos), Loukas Vyntra (Panathinaikos)
Midfielders: Costas Katsouranis (Panathinaikos), Giorgos Karagounis (Panathinaikos), Alexandros Tziolis (Racing Santander), Giorgos Fotakis (PAOK), Panagiotis Kone (Bologna), Grigoris Makos (AEK Athens), Thanos Petsos (Kaiserslautern)
Forwards: Stephanos Athanasiadis (PAOK), Angelos Charisteas (Panaitolikos), Georgios Samaras (Celtic), Dimitris Salpingidis (PAOK), Fanis Gekas (Eintracht Frankfurt)