Arsene Wenger’s men kick off their Group H campaign at the Emirates Stadium with the visit of the Bundesliga side, who attracted a huge following of away fans.
With kick-off approaching, it was reported that congestion around the stadium was causing delays and potential issues with safety.
The Gunners then confirmed the match had been put back by an hour.
The development is perhaps unsurprising given approximately 20,000 supporters are reported to have arrived in London for Cologne's return to European competition, despite only 3,000 tickets being made available to the club.
Earlier in the day, a large group of travelling fans brought the centre of the capital to a standstill as they congregated down Oxford Street.
UEFA did not rule out a further delay to proceedings when it tweeted the game would be held up by a 'minimum' of one hour.
Hopes that a kick-off off 9:05pm local time would be achievable were dented by the sight of riot police patrolling outside of the stadium, as well as video footage of skirmishes among the few people inside the ground.
Arsenal eventually confirmed the game would, indeed, go ahead at the revised time.