Ireland got the St. Patrick's Day celebrations at Sabina Park off to a rousing start, when they won the toss, chose to field, and dismissed Pakistan for 132 in 45.4 overs.
Pakistan's dismal performance means that the 1992 champions, who lost the opening game to West Indies, will be eliminated from the tournament if they lose to Ireland's part-timers.
Boyd Rankin was the most successful Irish bowler with three wickets for 32 runs from nine overs, Andre Botha supported with the flattering figures of 8-4-5-2, and Kyle McCallan collected two for 12 from 5.4 overs.
Only four Pakistani batsmen got into double-figures - Kamran Akmal scored 27, Imran Nazir got 24, and Mohammad Yousuf made 15, and Mohammad Sami gathered 12.
The Irish bowlers gained favourable bounce and movement from the hard, grassy surface, but the Pakistani batsmen were also victims of their own indiscretion and athletic fielding from their opponents.
Pakistan were set back from early, when Mohammad Hafeez was caught behind for four off Dave Langford-Smith driving loosely outside the off-stump in the first over, and Younis Khan was caught low at first slip for a duck off Rankin in the fourth over.
Pakistan were 15 for two, and Yousuf came out and added a valuable 41 for the third wicket with opener Imran Nazir with little worry.
They appeared to be getting on top of the bowling with both playing some delightful strokes through off-side, when Yousuf was caught at backward point off Irish captain Trent Johnson essaying a square drive in the 13th over.
This precipitated a mini batting collapse for Pakistan, as they also lost skipper Inzamam-ul-Haq, Nazir, and Shoaib Malik for the addition of 14 runs in the space of 43 balls.
Inzamam edged a forward defensive stroke and was caught at slip for one off Andre Botha in the 14th over, and the same bowler also struck when Nazir too, played forward defensively and edged to slip in the 18th over.
Pakistan slid to 72 for six in the 21st over, when Shoaib Malik played forward and inside-edged a catch to the keeper off Kevin OBrien. He made nine.
Azhar Mahmood, so late an inclusion in the Pakistan side that the official team sheets circulated to the media still had Danish Kaneria listed instead of him, came to the wicket and stemmed the fall of wickets with Akmal in a stand of 31 for the seventh wicket.
Rankin however, was brought back for a second spell from the northern end of the ground, and he removed them both in the space of four balls of the 31st over.
Both Mahmood, who scored two, and Akmal attempted pull shots, top-edged, and were caught in the arc between mid-wicket and mid-on to leave Pakistan on 103 for eight.
Mohammad Sami and Rao Iftikhar came together to temporarily halt the slide, but McCallan was given another spell from the southern end, and had Sami caught at long leg in the 44th over before Umar Gul was caught at deep mid-wicket for one to bring an end to the innings.
The Irish are playing an unchanged 11, but Pakistan brought Sami and Mahmood into their 11 for Rana Naved-ul-Hasan and Kaneria.
Pakistan lost the World Cup opener against West Indies by 54 runs on Tuesday at the same venue, but Ireland tied their opening match with Zimbabwe on Thursday.
West Indies lead the group with two points, Ireland and Zimbabwe have one point apiece, and Pakistan have no points, and they are in danger of not qualifying for the Super Eight quarter-final stage if they lose to the Irish.
Pakistan 132 all out 45.4 in overs (Kamran Akmal 27, Imran Nazir 24; Rankin 3 for 32, Andre Botha 2 for 5, McCallan 2 for 12) Vs Ireland (yet to bat)