Quentin Westberg made four saves to earn his third clean sheet of the season. The Toronto FC goalkeeper came up particularly big on a pair of late chances from Anthony Jackson-Hamel and Maximiliano Urruti, Westberg stopping both at close range.
It was a much-needed win for Toronto, who had posted just a 1-6-4 record in its previous 11 matches. The victory puts Toronto FC (7-8-5, 26 points) back over the playoff line and into seventh place in the Eastern Conference.
The Impact have lost their last three league games, and have conceded 19 goals over their last nine matches in all competitions.
After an hour of somewhat uneventful action, Pozuelo broke the deadlock in the 61st minute. The midfielder recorded his eighth goal of the season after collecting a turnover at midfield and taking the ball just outside the box, before firing a well-placed strike into the net.
Less than four minutes after Pozuelo's goal, the referee halted the match due to heavy rains and storms in the area. Play resumed after a 25-minute delay.
The Impact (9-10-3, 30 points) kept up the pressure down the stretch, though Altidore's free-kick goal sealed the result five minutes into stoppage time. It was Altidore's sixth goal in only 10 games, as the star forward's playing time has been limited due to injuries and international absences.
Altidore and Michael Bradley were both back in Toronto's lineup after missing the previous four games to the CONCACAF Gold Cup. The Impact also had Micheal Azira and Daniel Lovitz back from international duty, while Clement Bayiha came off the bench after an 11-game absence with a quad injury.
Omar Gonzalez started at center back in his Toronto FC debut. The veteran defender was playing in his first MLS match since 2015.