Sunderland's initial bid was rejected by AZ, but such is manager Paolo Di Canio's interest in the player that a second approach was always expected.
The Wearside outfit's interest in Altidore became apparent last night when a statement connecting him with a move to the Black Cats appeared on the player's official website, only to be removed within hours.
Altidore has previous Premier League experience having spent the 2009-10 season on loan from Villarreal at Hull.
He scored one league goal as the Tigers headed for relegation, and his English experience came to a premature end when he was sent off against Sunderland in the penultimate match of the season.
He had joined Villarreal from New York Red Bulls in 2008 but spent much of his contract with the Spanish side on loan elsewhere, with Xerez, Hull and then Bursaspor.
The striker agreed a permanent move to AZ in July 2011 and finished his first campaign in Holland with a haul of 22 goals in all competitions before adding 23 goals for the 2012-13 Eredivisie season, helping the club to a first KNVB Cup in 31 years.
Altidore has also scored 17 goals in 60 appearances for his country after making his senior debut in 2007. Having failed to score since November 2011, he ended a lengthy goal drought in an international friendly victory over Germany in Washington DC last month.
Altidore will join goalkeeper Vito Mannone, defenders Valentin Roberge and Modibo Diakite, midfielder Cabral and winger David Moberg Karlsson as part of Di Canio's new-look squad at the Stadium of Light.
SUNDERLAND FIXTURES:
Saturday August 17
15:00Premier League Sunderland v Fulham
Saturday August 24
15:00Premier League Southampton v Sunderland
Saturday August 31
15:00Premier League Crystal Palace v Sunderland
Saturday September 14
15:00Premier League Sunderland v Arsenal
Saturday September 21
15:00Premier League West Brom v Sunderland
Saturday September 28
15:00Premier League Sunderland v Liverpool
Saturday October 5
15:00Premier League Sunderland v Man Utd
Saturday October 19
15:00Premier League Swansea City v Sunderland
Saturday October 26
15:00Premier League Sunderland v Newcastle United