On March 1 ,2006 Fàbregas played his first game for the Spanish senior team, becoming the youngest player capped for Spain in 80 years. He received good reviews for his début , contributing an assist for Spain's first goal in a 3–2 victory over the Côte d'Ivoire.

On May 15, 2006, Fàbregas was selected for the Spanish World Cup squad. In the 2006 World Cup, he came on as a second-half substitute in Spain's first two group matches, contributing an assist in their 3–1 victory against Tunisia. He then started alongside Spain's reserve players (including then Arsenal teammate José Antonio Reyes) in Spain's third group match against Saudi Arabia. He earned a starting role in Spain's first knockout stage match against France in place of Marcos Senna, but Spain lost that match 3–1.

On June 14, 2006, Fàbregas became the youngest player in Spanish history to participate in a World Cup when he came on as a substitute for Luis García after 77 minutes in a 4–0 victory against Ukraine. He was then 19 years and 41 days old.