The former captain begins his new role from Monday, working alongside the Brazilian head coach while continuing his studies towards a full coaching licence.
In its official statement, the Catalan club explained the move: "Sergio Busquets joins Barça Atlètic as assistant coach from this Monday.
"The Barça legend returns to the club and joins Juliano Belletti's staff to put his experience and footballing knowledge at the service of the team, while completing the course to obtain his coaching badge."
Busquets came through La Masia and is one of the defining figures of Barcelona's most successful era. He made his first-team debut in 2008 under Pep Guardiola, quickly becoming the anchor of a midfield alongside Xavi Hernández and Andrés Iniesta that formed one of the most iconic trios in modern football.
Across more than 700 appearances in Barcelona colours, he won a host of trophies, including the club's most recent LaLiga title in 2023 under Xavi, before leaving to join Inter Miami and link up again with former teammate Lionel Messi.
Having wound down his career in the United States, the Spanish midfielder announced his retirement from playing in 2025. Now, just months later, he is ready to begin a new chapter of his career at the very club where he became a legend. His role will be to accompany and help develop the best talents coming through La Masia, passing on the philosophy and playing principles that helped define Barcelona's golden era to the club's next generation.
Busquets' arrival follows a well-worn path for former Barcelona greats moving into coaching through the club's academy structure, with figures including Guardiola himself having taken similar routes on their way to management.
For now, his focus is on completing his coaching qualification while gaining hands-on experience alongside Belletti, who led the club's Under-19 side to a treble of the Copa del Rey, División de Honor and UEFA Youth League titles before taking over at Barça Atlètic last season.