The Spain international scored 30 goals in 46 appearances in all competitions last season and will become Tottenham's record signing, with the fee believed to be around £26million.
Soldado will be Andre Villas-Boas' third addition of the summer, following on the heels of £17million Corinthians midfielder Paulinho and winger Nacer Chadli from FC Twente.
The 28-year-old started his career at Real Madrid but he made only 16 first-team appearances, spending a season on loan at Osasuna before being sold to Getafe in 2008.
He moved to Valencia in 2010 and netted 80 goals in 146 appearances for the club.
He made his Spain debut six years ago and scored six times in 11 appearances while he was part of the squad at June's Confederations Cup, where his country lost out to Brazil in the final.
Tottenham had previously been linked with Belgium striker Christian Benteke before he elected to sign a new contract with Aston Villa.