Contador was born in Pinto in the autonomous community of Madrid, the third of four children. He has an older brother and sister and a younger brother, who has cerebral palsy. Having previously practiced other sports, such as football and athletics, Contador discovered cycling at the age of 14 thanks to his elder brother Francisco Javier.
At the age of 15, Alberto began to compete in races at the amateur level in Spain, joining the Real Velo Club Portillo from Madrid. Although he got no victories that year or the next, he demonstrated great qualities and was soon nicknamed Pantani (after Marco Pantani, regarded as one of the best climbers of all time) for his climbing skills. In 2000, he experienced his first victories, winning several mountains classification prizes from prominent events on the Spanish amateur cycling calendar.
He dropped out of school at the age of 16 without having finished his Bachillerato and signed with Iberdrola-Loinaz, a youth team run by Manolo Saiz, manager of the professional ONCE cycling team. In 2001, he won the under-23 Spanish time trial championship.
Contador lives with his fiancée Macarena in the city of Madrid when not competing, and enjoys hunting in his spare time. He has a fascination for birds, keeping personally-bred canaries and goldfinches at home.