Gomez and Khedira are back after missing the previous set of internationals earlier this month.
The three-times champions have already qualified for next year's tournament but are eager to become the first Germany squad to win all their qualifiers for a major tournament.
Bundesliga top scorer Gomez has shaken off a nagging groin injury, scoring twice in midweek in Bayern Munich's 2-0 Champions League win over Manchester City.
"It was important for us to qualify early on and now we want to win these two qualifiers to have won 10 out of 10," said coach Joachim Low.
Low also called up Borussia Monchengladbach's attacking midfielder Marco Reus who has yet to make his debut after being ruled out with injury in his last three call-ups.
Germany, who top Group A with 24 points from eight games, travel to second-placed Turkey on October 7 before hosting Belgium four days later.
Turkey have 14 points, two ahead of Belgium.
Goalkeepers: Manuel Neuer (Bayern Munich), Tim Wiese (Werder Bremen), Ron-Robert Zieler (Hanover 96)
Defenders: Dennis Aogo (Hamburg SV), Jerome Boateng (Bayern Munich), Holger Badstuber (Bayern Munich), Benedikt Howedes (Schalke 04), Mats Hummels (Borussia Dortmund), Philipp Lahm (Bayern Munich), Per Mertesacker (Arsenal), Christian Trasch (VfL Wolfsburg)
Midfielders: Mario Gotze (Borussia Dortmund), Sami Khedira (Real Madrid), Toni Kroos (Bayern Munich), Thomas Muller (Bayern Munich), Lukas Podolski (Cologne), Mesut Ozil (Real Madrid), Marco Reus (Borussia Monchengladbach), Simon Rolfes (Bayer Leverkusen), Andre Schuerrle (Bayer Leverkusen), Bastian Schweinsteiger (Bayern Munich)
Forwards: Mario Gomez (Bayern Munich), Miroslav Klose (Lazio), Cacau (VfB Stuttgart).
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