Penalty king Tommy Miller kept his cool to earn a crucial three points for Ipswich's play-off hopes and dent Sunderland's chances of catching the top two.
Miller, who has never missed a spot-kick for Town, rammed home his 11th goal of the season in first-half stoppage time and a rare home clean sheet meant that was enough for the points, In a game of few chances the hosts were slightly more penetrative, and held Sunderland to just two fairly tame shots on target.
Early on, Miller fired over before Kevin Kyle dangerously flicked on a Sean Thornton corner, but Fabian Wilnis did well to clear.
Shefki Kuqi and Thornton both fired wide from distance, before a Jim Magilton corner found Darren Bent unmarked, but his header was blocked.
Gary Breen headed a Thornton corner over before Jermaine Wright had a shot blocked after a Sunderland defensive mix-up.
Town went ahead just before the break, Miller slotting home from the spot after Sunderland keeper Thomas Myhre caught Bent as both chased an Ian Westlake pass.
Bent dragged a good chance wide soon after the break before John Oster finally tested Kelvin Davis with a weak 25-yarder.
Town nearly doubled their lead when Westlake found Shefki Kuqi whose angled shot was booted off the line by Phil Babb.
Sunderland introduced former Ipswich hero Marcus Stewart to a warm ovation, but Town restricted him to just one header which looped harmlessly over.
Ipswich always looked dangerous on the break and Bent tested Myhre with a low drive before Davis leapt to save Thornton's free-kick.
That was the last real threat from the visitors and it was Ipswich who looked the more likely to score particularly in the last few seconds.
Bent, a threat all day, should have got the goal his display deserved, but incredibly had three goalbound shots blocked in the space of ten seconds.