Copenhagen stunned Russian rivals Rubin Kazan with a late winner at home in their UEFA Champions League opener on Tuesday to claim all three points.
Sharing Group D with Barcelona, who saw off Panathinaikos 5-1, Copenhagen were indebted to Senegalese striker Dame N'Doye, who headed the winner from a free-kick with just three minutes left.
Rubin pulled off a famous win over Barcelona in last year's tournament but still failed to get out of the group stage and that inconsistency was on show again in their 2010/11 opener.
Despite boasting the talents of Nigerian star Obafemi Martins and playmaker Carlos Eduardo, they were unable to break down a resolute home defence.
Copenhagen squeezed through a qualifier and a play-off to make this stage and looked unlikely to break through until N'Doye's late intervention.