Brought on as the fifth bowler after the hosts were put in on a bright, breezy afternoon, Shadab's mesmerising mixture of leg-breaks and googlies earned him figures of three for seven, the most economical ever in the history of T20 international cricket in a complete four-over spell.
World champions West Indies only managed to get into three figures thanks to an unbeaten 34 from captain Carlos Brathwaite.
He dominated a 37-run eighth-wicket partnership with fellow-Barbadian Jason Holder, who was dismissed off the last delivery of the innings.
Shadab removed opening batsman and wicketkeeper Chadwick Walton and dangerous middle-order strokeplayer Lendl Simmons in his first over before adding the scalp of Sunil Narine in his second.
Kamran Akmal, back in the national T20 side after an absence of three years, deprived the newcomer a fourth wicket when he failed to hold on to a diving catch at backward point offered by Kieron Pollard.
For all the struggles they faced against Pakistan's talented and varied bowling attack, the home side's troubles started when Evin Lewis was run out in the third over of the match by Ahmed Shehzad's direct hit from 40 metres out as the batsman attempted to complete a second run.
Marlon Samuels, man of the match in two World T20 finals, was unfortunate to be adjudged leg-before to Pakistan's other slow bowler, Imad Wasim.
Thereafter it was a combination of impatience and poor shot selection which the visitors capitalised upon to take the advantage at the halfway point of the match.
Rovman Powell, like Shadab making his T20 International debut, failed to have an immediate impact with the bat as he fell to fast-medium bowler Hasan Ali.
He and the other bowlers in the West Indies line-up now face a formidable challenge to prevent Pakistan taking a 1-0 lead in the series and extending their winning streak in T20 Internationals against the Caribbean side to four.