The hosts were all out for 145 in 19 overs in Lahore, with Mark Wood (3-20) leading the way for England, who fell just short despite Moeen Ali’s half-century off 35 balls.
Jamal claimed his maiden international wicket on just the second ball of his career and, under immense pressure, the youngster held his nerve to steer Pakistan to a tense win.
Wood’s fierce pace had put England in command as he removed half of Pakistan’s top six, with Babar Azam (9), Haider Ali (4) and Asif Ali (5) failing to reach double figures.
Mohammad Rizwan top-scored for Pakistan with 63 from 46 – his fourth half-century this series – but David Willey (2-23) and Sam Curran (2-23) restricted the home side’s total.
Chris Woakes, making his first appearance since March, wrapped things up thanks to a swipe from Haris Rauf (8) as England were set a more-than-gettable target of 146.
However, opener Alex Hales went inside five balls for just a single run and fellow opener Phil Salt (3) pulled a short ball straight into the hands of Rauf soon after.
The tourists struggled for momentum, with Harry Brook (4) and Dawid Malan (36) trapped lbw after Ben Duckett (10) spooned Mohammad Wasim’s short ball to Shan Masood.
Curran (17) sliced Jamal’s second ball to Wasim as England chased boundaries, with Woakes (10) close behind, but Moeen kept his side ticking along.
England required 15 from the final six balls and would have forced a super over had David Willey cleared the boundary off the last ball, but it was not to be as Jamal held his nerve.