Koscielny was a doubt for Tuesday’s play-off round first-leg tie in Turkey after taking a knock to his Achilles in the 2-1 win over Crystal Palace on Saturday night.
However, Kieran Gibbs did not train and has been ruled out with a hamstring injury which is expected to keep him sidelined for up to three weeks.
Callum Chambers is likely to continue alongside Koscielny in the centre of defence. Per Mertesacker was on standby to replace Koscielny but took no part in the session at London Colney.
Mertesacker and his fellow World Cup winners Mesut Ozil and Lukas Podolski are still on extended leave
Arsenal fly out to Istanbul on Monday afternoon and you can watch Arsene Wenger's news conference from the Ataturk Stadium this evening on Sky Sports News HQ.
Those training top colours are shocking. The only Arsenal top that should have green or light blue on it should be a keeper jersey- outrun