Rangers have been fined £8,280 by Uefa for the behaviour of their fans during their match against Osasuna - but the Spanish club must pay £31,000.
The control and disciplinary section of European football's governing body said there were "serious deficiencies in the organisation of the game" by Osasuna.
Uefa added that there was "improper conduct" by both sets of fans at the Uefa Cup tie in Pamplona on 14 March.
It is thought that Rangers' fine was largely for fans' sectarian singing.
The two clubs have three days in which to appeal against the decision.
Rangers said on their website: "We expect to receive the full reasons for the judgement from Uefa in the next few days.
"Uefa has acknowledged the great efforts the club and our supporters have made in tackling sectarianism""The club understands that the penalty reflects mainly discriminatory singing at the end of the match.
"However, we believe that, in coming to their decision, Uefa has acknowledged the great efforts the club and our supporters have made in tackling sectarianism with measures including the fans' self-policing drive.
"We also understand Uefa has listened carefully to the very strong case the club and its supporters made in relation to the treatment of fans at the match and the woeful segregation arrangements."
Their last-16 match was played with a backdrop of violence in the stands as Rangers supporters clashed with Spanish police.
Many travelling fans accused the police of heavy-handed tactics, or even brutality.
But the Glasgow club admitted shortly after the second-leg match, which Walter Smith's side lost 1-0 to go out of Europe, that several supporters who were banned from Ibrox had made the trip to Spain and gained entry to the El Sadar Stadium.
Thousands of visiting fans obtained tickets on the black market for the match.
Footage - which emerged on the YouTube website - of Rangers supporters involved in sectarian chanting at the match was also examined by Uefa.
And chairman Sir David Murray said he would consider refusing tickets for away matches in Scotland and for European games if fans continued with distasteful chanting.
But Rangers had feared a heavier punishment, particularly after being fined £13,000 for a similar offence last season following their Champions League clash with Villarreal.
Uefa's website stated: "Osasuna have been fined 45,000 Euros for serious deficiencies in the organisation of the game on 14 March, as well as for the improper conduct of their supporters.
"Rangers, meanwhile, have been ordered to pay 12,000 Euros for the latter offence involving visiting fans of the Scottish team."
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