A Boston Bruins fan says he was beat up and called homophobic slurs at an Avalanche game in Denver last week ... and cops have confirmed to TMZ Sports they're now investigating it all.
Cadien Shaw told ABC 7 the interaction with Colorado fans at Ball Arena following the Bruins' loss to the Avs on Jan. 26 began innocently ... but then he claims it soon got heated.
Shaw said 3 men approached him ... and after some words, they began to make inappropriate comments about his sexuality.
"It turned to aggressive homophobic slurs," Shaw said.
Soon after, Shaw said the men tackled him, kicked him, and repeatedly called him anti-gay slurs. Shaw said he suffered knee, elbow, and head injuries in the altercation.
Cops tell us they are investigating the alleged incident, saying its Bias Motivated Crime Unit is handling the probe. Police added they're urging any witnesses to contact them.
Shaw, meanwhile, was clearly disappointed and hurt over the situation ... but he did say he would return to Ball Arena if his beloved Bruins were playing.