Born in Cairo on 1 January 2008, Hamza Abdelkarim joined the youth team at Egypt's most successful club Al-Ahly in 2020. He moved through the youth levels until he was called up to the first team squad for the first time in January 2025. His debut came on 6 February, when he became the youngest player to appear for the club in the 21st century, aged just 17 years old.

On 1 February 2026 he joined the blaugranes on loan until the end of the season. Administrative issues meant he couldn't play until 8 March, but on his debut with the U-19A side he scored a goal away at Huesca.

He went on to play nine league games, scoring six goals, including a hat-trick in the massive 9-0 win against Montecarlo (9-0) on the day the team won the Liga de División de Honor. He also made two appearances in the Copa del Rey, with Barça finishing runners-up.

In summer 2026, Barça signed him on a permanent transfer and he was part of the 2026/27 preseason squad for Hansi Flick. His four goals made him top scorer in preseason. On 31 August 2026, he made his competitive debut for FC Barcelona against Rayo Vallecano at the Spotify Camp Nou.

On the international stage, he first represented Egypt at U-17 level. He was part of the squad for the 2024 UNAF U-17 tournament and the 2025 U-17 African Cup of Nations, before being called up by the full side for the 2006 World Cup, where he made four appearances.