Celton Biai was born in Lisbon on 13 August 2000 to a Bissau-Guinean family and came through the Benfica youth system as a goalkeeper, working his way up to the B side that competed in the Portuguese second tier. Tall and quick off his line, he was regarded as one of the more promising keepers of his age group at the Seixal academy.

First-team opportunities never arrived, and in 2020 he moved to Vitória de Guimarães, where he progressed from the reserve team to the senior squad and made his Primeira Liga debut. In January 2024 he left Portugal for the Netherlands with Dordrecht, and the following year joined Excelsior. He has represented Guinea-Bissau at international level.