After only a few Segunda División matches, Pablo received his first call-up to the Spanish under-21 team, for a friendly match against Bulgaria on 19 November 2002. Despite the media's assumption that he would be among the substitutes, he played the whole match as Spain won 7–1. He was a regular selection over the next 12 months, and finished his under-21 career with ten caps. His last appearances came as Spain were eliminated by Sweden in the qualification play-offs for the 2004 European Under-21 Championships.