Yousuf's 107 helped steer Pakistan away from danger after they stuttered to 140-4 but were able to recover to 265-4 when the light forced play to close 21 overs early.
The home team now has a lead of 59 runs over the West Indies first innings total with six wickets in hand.
The 32-year-old Yousuf, who hit a double hundred and two hundreds on Pakistan's tour of England earlier this year, added 125 runs for the fifth wicket with Shoaib Malik who was not out on 61.
The partnership set a new fifth wicket record against the West Indies, surpassing the 115 Shahid Afridi and Asim Kamal had set in Barbados last year.
Yousuf punished the West Indies for a lack of execution in the field after he was dropped on 43 by Daren Ganga and then by Jerome Taylor when he reached 101.
The batsman, who had already completed 1,000 runs in the calendar year, has now hit six hundreds in 2006 and this becomes his fourth hundred in the last five Tests.
"I am happy that I have scored a hundred when the team needed it," Yousuf said.
"The year has been superb for me and I thank Almighty, my captain and the team for their support," said Yousuf, who sympathised with bowlers around the world.
"I have playing cricket for eight to ten years and most of the wickets are flat where bowlers toil hard. I think wickets should be supporting where both batsmen and bowlers should have equal chance."
The West Indies had fought back by dismissing opener Mohammad Hafeez (57) and Inzaman-ul-Haq for a duck in his return match from suspension.
But as the West Indian attack failed to get any life from the pitch, Yousuf started to clock up the runs.
When Mohammad he reached 32, the batsman overhauled Salim Malik's 5,768 Test runs to become third-highest run-getter for Pakistan, behind Javed Miandad (8,832) and Inzamam-ul-Haq (8,498).
The test continues tomorrow.