Born in Santos, São Paulo, Kaiky joined Santos' youth setup from local side Portuários.[1] Initially playing futsal, he started to appear in the club's football categories at the age of nine.[2]
On 21 December 2020, Kaiky signed his first professional contract with Peixe, agreeing to a three-year deal.[3] He made his professional debut the following 28 February, starting in a 2–2 Campeonato Paulista away draw against Santo André.[4]
On his Copa Libertadores debut on 9 March 2021, Kaiky started and scored his first professional goal, netting the winner in a 2–1 home success over Deportivo Lara;[5] aged 17 years, one month and 25 days, he became the youngest Brazilian to score in the competition and second overall, only behind Juan Carlos Cárdenas;[6] his record was broken in the following month by teammate Ângelo.
Kaiky made his Série A debut on 29 May 2021, starting in a 0–3 away loss against Bahia.[7] On 27 April 2022, after establishing himself in the first team squad, he renewed his contract until December 2026.[8]
Almería
On 11 July 2022, Santos agreed to transfer Kaiky to Spanish La Liga side UD Almería for a rumoured fee of €7 million.[9] The move was officially announced eight days later, with the player signing a six-year deal.[10]
Kaiky made his debut abroad on 14 August 2022, starting in a 2–1 home loss to Real Madrid.[11] He scored his first professional goal on 26 August 2023, netting a last-minute equalizer in a 1–1 away draw against Cádiz.