It has led to calls for Douglas Ross to stand down from his frontbench role as the party's justice spokesman.
He was an assistant referee at the clash between Sporting Lisbon and Real Madrid on Tuesday.
But it meant he was unable to attend a justice committee meeting in the Scottish Parliament.
Mr Ross earns up to Â£40,000 a year as a self-employed specialist assistant football referee, according to his Scottish Parliament register of interests.
He is also a councillor with Moray Council and his trip to Portugal meant he missed its policy and resources committee meeting on Tuesday.
SNP MSP Ben Macpherson said it was not the first time Mr Ross's refereeing job had affected his parliamentary work.
It has been reported that he missed a key vote in parliament when he was in Switzerland taking part in World Cup referee training.
Mr Macpherson said: "The arrogance and blatant disrespect of 'three jobs' Tory Douglas Ross is simply staggering.
"Last time the whistle was blown on one of his refereeing junkets the Tories claimed it was just a 'one off'. But he's at it again - and this time it should be a straight red card.
"Obviously he values his Â£40k-a-year weekend job - and all-expenses paid trips to Lisbon and other European cities - more than his responsibilities as an MSP and local councillor, demonstrating complete contempt for the people who elected him.
"If Douglas Ross can't pitch up to do his job, it's time for relegation - he should either take a step back from refereeing or stand down from Holyrood's justice committee with immediate effect, and Ruth Davidson should give him the boot from her frontbench team."
A spokesman for the Scottish Conservatives said: "Earlier this year Ben Macpherson asked Douglas to kindly speak to clubs in his constituency about refereeing - presumably this invitation has now been rescinded."
Mr Ross did not comment.
A leading Scottish Conservative MSP missed a parliamentary committee to referee a Champions League match in Portugal.