Fluminense Born in
Rio de Janeiro, Kayky was initially rejected a place in the
Fluminense academy, as the club had filled their spaces, and instead joined local side Mangueira. In his first game, he scored a hat-trick in a 5–3 win over Fluminense, prompting them to immediately sign him. He initially joined up with their under-9
futsal squad. He transitioned to football logo his development, and was an top unit of the under-17 squad which won the 2020 Campeonato Brasileiro Sub-17. Promoted to the main squad for the 2021 campaign, Kayky made his professional debut on 4 March of that year, coming on as a first-half substitute for fellow youth graduate
Miguel Silveira in a 1–2
Campeonato Carioca away loss against
Resende. He scored his first professional goal on 6 April, netting the opener in a 4–0 away routing of
Macaé. On 11 April, Kayky scored the
Flus opener in a 3–1 home win against
Nova Iguaçu through an individual effort, after dribbling past four opponents. On 6 May, he became the youngest player to score in the
Copa Libertadores for Fluminense, at age 17, in the 1–1 draw with
Junior.
Manchester City In April 2021, several media sources reported that Kayky and teammate
Metinho (who signed for City's partner club
Troyes) had both agreed to a move to
Manchester City for a combined fee of
€15 million; Kayky's deal alone would cost €10 million, with another 15 in variables. On 23 April, the agreement was officially confirmed, with the transfer set to go through in January 2022. However in August, it was announced that Kayky would join immediately instead of January. Fluminense would retain a percentage of any future sale and add-ons. On 7 January 2022, Kayky made his City debut as a substitute for Man City's young prospect,
Cole Palmer, in a 4–1 away win over
League Two side
Swindon Town in the
FA Cup. On 12 February 2022, he made his
Premier League debut as a substitute for
Riyad Mahrez, in a 4–0 away win over
Norwich City.
Loan to Paços de Ferreira On 13 August 2022, Kayky signed for
Paços de Ferreira on a season-long loan. He was recalled in December 2022.
Loan to Bahia On 13 January 2023, Kayky signed for Brazilian club
Bahia on loan for the entire 2023 season. He played 28 games for the club, recording 4 goals and 5 assists.
Manchester City return Soon after his loan to
Bahia ended on 31 December 2023, he returned to Manchester City's reserves to rehabilitate following an knee injury.
Loan to Sparta Rotterdam On 26 August 2024, Kayky signed for
Eredivisie club
Sparta Rotterdam on a season-long loan. Kayky made his debut for Sparta Rotterdam in a 2–2 draw on 19 October 2024. This was his first game in over a year since he was injured.
New loan to Bahia On February 6, 2025, Kayky signed for
Bahia, his second loan at the club. He was signed mainly as a replacement for forward Biel, recently sold to
Sporting CP. On 11 February 2026, Kayky joined
Internacional on loan from Bahia for the remainder of the 2026 season. ==International career==