The out-of-contract Republic of Ireland international, who missed much of last season with a shoulder injury, has become surplus to requirements at the Stadium of Light with Vito Mannone establishing himself as number one and Oscar Ustari providing the back-up since his arrival from Almeria in January.
Press Association Sport understands 29-year-old Westwood, as expected, has not been offered a new deal and will now look to resurrect his career elsewhere after a largely frustrating three years on Wearside.
The former Manchester City youth player joined the Black Cats on a free transfer from Coventry in July 2011, but managed just 24 senior appearances for the club with Simon Mignolet standing in his way for much of that time.
Mignolet's big-money departure for Liverpool last summer opened the door once again for Westwood, who had initially established himself as Ireland's number one in the wake of Shay Given's international retirement before a lack of first-team football persuaded then manager Giovanni Trapattoni to turn to Millwall's David Forde.
Westwood started 11 games for the club last season before injury struck in November, and has not been seen since.
News of Westwood's departure comes just a day after full-back Phil Bardsley severed his links with the club to join Stoke.
Sunderland remain in talks with midfielders Jack Colback and Sebastian Larsson, who are also out of contract, although Colback in particular has suitors with derby rivals Newcastle among them.
Source : PA
Source: PA