Born in Osasco, São Paulo, Kelvyn joined Internacional after a trial period in 2016, but was subsequently loaned to SER Santa Rosa before joining Atlético Tubarão's under-20 squad.
He made his debut for the latter's first team on 30 September 2018, starting in a 5–1 Copa Santa Catarina home routing of Operário de Mafra.
On 29 April 2020, after appearing with the main squad, he signed a permanent contract until December 2021.
[1] Kelvyn made his Série A debut on 4 October 2020, by coming on as a second-half substitute for Alyson in a 1–2 away loss against Palmeiras.
His first goal in the category came on 14 November, as he scored his team's first in a 2–4 loss at Grêmio.