He is on the books of Real Betis B and wears shirt number 22. His main role on the pitch is Forward. His estimated market valuation currently stands at 200K €.

His latest transfer saw him join Real Betis B from Real Madrid Castilla via Free on 2025-07-25.

During the Primera Federación 2025-2026 campaign, Borja Alonso made 24 appearances, scoring 5 goals and adding 0 assists. He averaged 0.2 goals per match from 0 shots, with 0 on target.