Fulop has played 50 games for Sunderland but has been out of the limelight since Craig Gordon joined the club for £9m three years ago.
He featured three times for Manchester City last season after signing on an emergency loan deal in April.
Sunderland boss Steve Bruce had revealed Town were in talks with the keeper two weeks ago, but the player and club have only just reached an agreement.
Still think Murphy will be in net on Saturday as Fulop will need to meet his team mates before lining up with them Blue Monkey Fulop will face competition for a starting position at Ipswich from Brian Murphy and Arran Lee-Barratt.
Veteran stopper Richard Wright was released at the end of last season after losing his first-team berth to 27-year-old Irishman Murphy.
It is the second time Town manager Roy Keane has returned to his former club for a player this summer, after clinching midfielder Conor Hourihane, 19, who signed a one-year deal in July.