Harewood, 34, has been in discussions with Pools after becoming a free agent a fortnight ago when he left Bristol City.
Hartlepool manager Colin Cooper, who was a team-mate of the forward during his playing days at Nottingham Forest, will now look to involve the experienced front-man against Fleetwood Town this Saturday.
Harewood will wear the No 9 shirt vacated by Steve Howard and returns to the North-East where he scored five goals in 15 loan appearances during Newcastle's promotion to the Premier League in 2009-10.
He started his career at Forest before moving to West Ham United in a £500,000 deal in 2003. He stayed at Upton Park until Aston Villa paid £4m for him in 2007.
Harewood then went on to have loan stints at Barnsley, Blackpool and Forest before a short spell in China with Guangzhou and then he switched to Bristol City last summer.
Hartlepool have not revealed the length of the contract Harewood has signed at Victoria Park, but he will be at the club until the end of the season at least.