Although Sneijder came through the Ajax youth academy, he is not a native of Amsterdam. He was born in Utrecht and hails from a football family: his father was a talented player and his older brother Jeffrey plays for Stormvogels Telstar. There's also a younger Sneijder brother, Rodney Sneijder, who is likely to turn professional. Journalists have dubbed him the "patient pitbull".

Sneijder made his debut for Ajax in a 2-0 win at SC Excelsior on 22 December 2002 when manager Ronald Koeman, troubled by an injury-filled squad called him up, advised by Danny Blind, the then-coach of the Ajax youth-squad. He rapidly established himself in the role of midfield general and occasional left winger. Despite his slight stature, he is strong on the ball and his passing range is enhanced by his two-footedness. He is also a free kick specialist and finished the Eredivisie 06/07 season with a tally of 18 league goals.

On August 12, 2007 Ajax agreed to sell Sneijder to Real Madrid for 27 million euros, according to the club's web-site, making this transfer runner-up in the Dutch football transfer record list of all times. He was the second of three Dutchmen to sign for Real Madrid for the 2007 season joining Royston Drenthe and later Arjen Robben. In his first La Liga match for Real Madrid he scored the winner in the Madrid derby against Atletico Madrid.