Samuels took the attack to Pakistan, supported by captain Brian Lara, before both fell to off-spinner Mohammad Hafeez whose spell of two for 39 held back West Indian progress.
A swashbuckling knock of 32 from 15 balls by number eight Dwayne Smith boosted the final total, though, giving Lara's side a competitive target to defend.
Pakistan made a promising start, picking up the wicket of West Indies opener Chris Gayle in the third over when the left hander was caught behind by Kamran Akmal off the bowling of Umar Gul for two.
Ramnaresh Sarwan was then dropped by Younis Khan off his first ball when he slashed wildly at a Gul delivery outside off stump.
Having survived that scare, Sarwan went on to lay the foundations for the West Indies.
Shivnarine Chanderpaul was brilliantly caught behind by Akmal off Rao Iftikhar for 19 with West Indies having progressed to 64.
However, Sarwan continued to look solid until he paid the price for a loose shot and was caught by Younis Khan for 49 off the impressive Iftikhar.
Iftikhar had been characteristically economical, bowling a tight line, but Marlon Samuels decided to take him on in the 28th over and drove a majestic straight six followed by a crashing four through extra cover to change the momentum.
Samuels produced some fine strokeplay, bringing up his fifty off 56 balls with a straight six off Shoaib Malik.
His partnership with Lara took the hosts to 168 before Lara was caught behind off Hafeez for 37.
But just as he threatened to take his team on to a big total Samuels holed out to Malik on 63 with six overs remaining.
Smith's rapid 32, including a spell of three overs where he and partner Dwayne Bravo put on 38 runs, restored West Indies impetus and left Lara's side with a fighting chance of victory.
West Indies 241 for 9 in 50 overs (Samuels 63, Sarwan 49, Lara 37, Smith 32, Chanderpaul 19; Iftikhar Anjum 3 for 44, Gul 2 for 38, Mohd Hafeez 2 for 39) Vs Pak (yet to bat)