(as) proud as a peacock

Proud to the point of arrogance, vanity, or boastfulness. Tom's been as proud as a peacock ever since he found out he came in top of the class—he hasn't missed a single opportunity to remind us. He looks like a total douchebag, strutting around the club proud as a peacock in his cheap suit and gold chains.

overly proud; vain. (*Also: as ~.) Mike's been strutting around proud as a peacock since he won that award. I sometimes think Elizabeth must spend all day admiring herself in a mirror. She's as vain as a peacock.

Having a very high opinion of oneself, filled with or showing excessive self-esteem. For example, She strutted about in her new outfit, proud as a peacock. This simile alludes to the male peacock, with its colorful tail that can be expanded like a fan, which has long symbolized vanity and pride. Chaucer used it in The Reeve's Tail: "As any peacock he was proud and gay." [1200s]

Having an exceedingly high opinion of oneself—one’s dignity or one’s importance. The comparison to a peacock, believed to allude to its strutting gait, dates from the thirteenth century. Chaucer used the simile several times, and it has often been repeated. “The self-applauding bird the peacock” is how William Cowper described it (Truth, 1781).