[1] Born in La Teste-de-Buch in Gironde, Serin began his career with nearby club Bordeaux Bègles in the Top 14.

He started the first match at scrum-half, paired with Jules Plisson at fly-half, and received praise from coaches, players, and the press despite being in the losing side (30-19).

They won that game 0-27 in what was Guy Novès's first away win as France manager, with Serin shining again.

He was then included in the 2016/17 30-man "elite" list, made of players selected by the French national team to be protected and not allowed to play more than 30 games that year.

France ended the series with a 19–24 loss to world champions New Zealand, in which Serin came onto the pitch during the second half and gave a remarkable out-the-back pass for Louis Picamoles to score the only French try of the game.