Lara ended a dismal run of low scores by hitting 48 as West Indies maintained their recent improvement in a tense encounter at the Gabba.
In reply to Pakistan's total of 197 in 49.5 overs, West Indies scored 198 for 4 with 11 balls to spare.
Carl Hooper, batting one place below Lara at No 5, scored an unbeaten 54, his 20th in limited-overs internationals, to guide his side to victory.
Hooper was joined by Jimmy Adams in an unbroken fifth-wicket partnership worth 74 runs. Adams contributed a valuable 33.
Lara, who has endured a miserable Test series against Australia, scoring a paltry seven runs in his last four innings, finally found some touch and timing. But the world record holder for the highest score in Test cricket almost found himself back in the pavilion with another failure to his name after a tentative start.
The West Indies vice-captain was fortunate to survive a huge appeal for leg before after playing back in his crease to a yorker from Mohammad Zahid. Coming back into the attack for a second spell of extreme pace, Zahid accounted for Lara when the left-hander offered a catch off the bottom edge to the wicketkeeper Moin Khan.
Sent into bat by the West Indies Courtney Walsh, Pakistan stumbled to 47 for 4 on a lively pitch before Ijaz Ahmed steadied their nerves with a patient 59 off 122 balls. Ian Bishop took for 4 for 38 with his pace bowling.
WORLD SERIES (Brisbane): Pakistan 197 (Ijaz Ahmed 59; I R Bishop 4-38); West Indies 198 for 4 (C L Hooper 54no). West Indies win by six wickets. Standings: 1 West Indies (P4, Pts4); 2 Australia (4-4); 3 Pakistan (4- 4).Reuse content