The 31-year-old has been a big success story at the County since joining after a stint in the Yorkshire leagues in 2013.
He made an immediate impact, playing a key role as the Steelbacks claimed glory in the T20 competition.
Azharullah has continued to establish himself as one of the most skilful white-ball bowlers in the country with controlled swing and a devastating yorker to baffle the best batsmen.
The seamer finished 2014 as the club’s leading wicket taker in the County Championship and went on to claim a further 45 first-class wickets the following season.
The right-arm quick has taken an impressive 172 first-class wickets for Northants in 58 appearances, also claiming 53 List A wickets and a total of 70 T20 scalps during his time at the club.
Northants chief executive Ray Payne said: “We’d like to thank Azhar for his contribution to what has been a very successful four years for the club.
“He has proved to be a great addition to the squad and has played an integral role in our achievements.
“I’d like to personally thank him for his services to the club and wish him all the best for his future endeavours.”