The visitors picked up the wickets of Hafeez (57) and captain Inzamam-ul-Haq for a duck in the space of seven runs to claw their way back into the match after being bowled out for 206 on the first day.
Hafeez, who made his third half century in his fifth test, added 88 runs for the third wicket with the in-form Yousuf before he was trapped lbw by a fast yorker from Jerome Taylor.
Inzamam came in with the total on 133 and survived a close lbw call first ball before being bamboozled by a sharp turning delivery from spinner Dave Mohammad which came in and hit his off-stump.
The Pakistan skipper, playing his first game after being banned for four one-dayers by the International cricket Council in September for bringing the game into disrepute, misread the flight of his eighth delivery and stretched helplessly forward.
Left-arm chinaman spinner Mohammad caused huge problems on a pitch taking turn.
Yousuf also survived a dropped chance with his score of 43 when Daren Ganga could not latch on to a sharp catch at gully off Taylor.
On a pitch which is slow but offering assistance to the seamers and spinners, Hafeez and Yousuf batted fluently despite the early loss of Younis Khan.
Resuming on 39 for one, Younis fell for 11 with the total on 45 when he mistimed a pull off Fidel Edwards straight to Ramnaresh Sarwan at short mid-wicket.
Hafeez and Yousuf than combined solid defence with delicate strokes as the West Indies bowlers conceded 88 runs from 142 balls.
Hafeez hit six fours. Yousuf was unbeaten on 50 at lunch, reaching his 26th half century from 67 balls with eight fours.
Shoaib Malik had yet to score.