Prolific Yousuf soared past West Indian Vivian Richards's 30-year-old landmark of 1,710 runs in a year and was unbeaten on 113, his second century of the match, to take the home team to 339-3 at tea at the National Stadium here on Thursday.
Pakistan, who resumed at 130-2, now have an overall lead of 383 with captain Inzamam-ul-Haq on 31 not out at the break and with a 1-0 lead overall are looking to secure the three-match series.
Stylish right-hander Yousuf added 149 runs for the third wicket with Mohammad Hafeez whose watchful and valuable innings of 104 was overshadowed by Yousuf's record-breaking feats.
Yousuf drove West Indian paceman Corey Collymore to long-on for his ninth boundary to cross Richards' record tally made in 1976. The 32-year-old achieved the new mark in 11 Tests, the same number it took the West Indian great.
After lunch, free-flowing Yousuf hit paceman Dwayne Bravo for his 14th boundary to reach his 23rd Test century off just 125 balls - his ninth century of 2006.
In the process he broke his own record of eight Test centuries in a year, which he achieved with his 102 runs in the first innings, breaking the previous mark of seven held jointly by Richards and Sri Lankan Aravinda de Siva (1997).
Yousuf also became the sixth Pakistani batsman to score a century in each innings of a Test, following Hanif Mohammad, Javed Miandad, Wajahatullah Wasti, Inzamam and Yasir Hameed.
When on 43 Yousuf further surpassed the Pakistan record for the most runs in a three-match series, set by former great Zaheer Abbas with 583 made against India in 1978.
It becomes his fourth hundred in five innings against the West Indies since his 192 in Pakistan's nine wicket win in the first Test in Lahore. He also made 191 in the drawn second Test at Multan.
The West Indies were again sloppy in the field as Daren Ganga grassed Yousuf in the penultimate over before lunch off part-timer Ramnaresh Sarwan when the batsman was on 68.
Paceman Jerome Taylor then spilled a simple chance off his own bowling when Yousuf was on 87. Yousuf once again capitalised on the fumble to punish the West Indian bowlers.
Hafeez, also dropped by Bravo on 103, reached his second Test century with his tenth boundary off Taylor before the fast bowler forced an edge for Denesh Ramdin to take a catch behind the stumps.
Pakistan 304 and 339 for 3 (Mohammad Yousuf 113, Mohammad Hafeez 104, Younis Khan, Inzamam-ul-haq 31; Gayle 1 for 38, Taylor 1 for 60) Vs West Indies 260