[8] Garuba helped Real Madrid win the final tournament and joined MVP Mario Nakić on the All-Tournament Team.

[10] In the 2018–19 season, he continued to primarily play for Real Madrid B, averaging 14.6 points, 12.0 rebounds, 2.1 assists and 1.5 blocks per game over 22 Liga EBA appearances.

[11][12] On 28 October 2018, at 16 years and seven months of age, Garuba debuted for Real Madrid in the Liga ACB, the first-tier league in Spain, against Miraflores.

He became the youngest center in ACB history, surpassing José Ángel Antelo, and the third-youngest Real Madrid debutant, behind Luka Dončić and Roberto Núñez.

In his season debut against Joventut Badalona, at 17 years, six months and 19 days of age, he eclipsed Dončić as Real Madrid's youngest-ever starter.

[15] On 30 October 2019, Garuba made his EuroLeague debut, recording 12 points, four rebounds, three steals, and a Performance Index Rating (PIR) of 20, against Bayern Munich.

[21] On 29 April, he recorded a career-high 24 points, 12 rebounds and 30 PIR, leading Real Madrid to an 82–76 win over Anadolu Efes in game 4 of the EuroLeague Playoffs.

[26] On 26 January 2022, the Houston Rockets announced that Garuba had undergone successful surgery to repair his fractured left wrist and was expected to be sidelined for six to eight weeks.

[37] In the summer of 2017, Garuba was unable to return to national team duty because he was recovering from a knee injury suffered earlier that year.

[3] At the 2018 FIBA U16 European Championship in Novi Sad, Serbia, he averaged 16.3 points and 12.3 rebounds per game and led Spain to a silver medal, earning a spot on the All-Star Five.

[38] Garuba helped Spain win a gold medal at the 2019 FIBA U18 European Championship in Volos, Greece, joining his teammate and MVP Santi Aldama on the All-Star Five after averaging 15.6 points, 12.9 rebounds and 2.1 blocks per game.

[39] In 2021, Garuba played on Spain men's national basketball team at the 2020 Summer Olympics in Tokyo, Japan[40][41] which were delayed by one year due to the ongoing COVID-19 pandemic.