Fast bowler Patel grabbed three wickets and left-arm seamer Pathan two as England crashed to their lowest-ever total of 125 against India after being put in to bat in the opening Group-A league match Sunday.
England's previous lowest against India in one-day internationals was 149 in a World Championship match at Sydney in 1985.
England then bowled brilliantly to make India struggle to achieve a modest 126-run target, with pacemen Steve Harmison and James Anderson, and off-spinner Jamie Dalrymple grabbing two wickets apiece.
Anderson removed pinch-hitter Pathan and skipper Rahul Dravid in the space of four balls and Dalrymple dismissed Mahendra Dhoni and Suresh Raina in the space of three balls to give a few anxious moments to India.
The hosts eventually emerged winners with 20.3 overs to spare, with Yuvraj Singh (27 not out) completing the job under lights to the delight of a sizeable holiday crowd.
Star batsman Sachin Tendulkar, making a record 368th appearance in one-day internationals, made a 41-ball 35 before being trapped leg-before to become Harmison's second victim.
A dismal batting performance sealed England's fate, with none crossing the 40-mark. All-rounder Paul Collingwood top-scored with 38, followed by Ashes hero Kevin Pietersen (27) and Dalrymple (24).
Man-of-the-match Patel and Pathan needed less than 13 overs of disciplined pace to put pressure on a new-look England batting order, reducing the tourists to 27-4 to ensure their team did not chase a stiff target.
England could never recover from a hat-trick of lbws, with Ian Bell, skipper Andrew Flintoff and Michael Yardy failing to reach double-figures.
Patel finished with a career-best haul of 3-18, while left-arm seamer Pathan bagged 2-20 after being out of form since the West Indies tour in May.
Offspinner Ramesh Powar grabbed three of the last five wickets to finish with 3-24, his best in one-day internationals.
India, under pressure after winning just two of their last nine one-dayers, were fortunate to run into an England side struggling in the shorter version of the game in recent months.
England had caved in even before Dravid introduced his spinners, who were expected to play a key role in the contest. Off-spinners Harbhajan Singh and Powar came in to bowl after England were wobbling at 55-5.
England, missing key batsmen Michael Vaughan and Marcus Trescothick, were jolted in the fourth over when make-shift opener Bell was trapped leg-before by Patel.
The tourists suffered a big blow when Flintoff fell for a duck in his first match in six months due to an ankle injury. The England skipper promoted himself in the batting order, but could last just seven balls.
Yardy contributed four runs before falling to Patel while Strauss was brilliantly held by Dravid at second slip off Pathan.
Pietersen fell to a low catch at first slip by Tendulkar after making 27, while Collingwood was caught by wicket-keeper Dhoni off Powar after hitting six fours in his 54-ball knock.
World champions Australia and the West Indies are other teams in Group A. South Africa, New Zealand, Pakistan and Sri Lanka are in Group B. The top two sides from each group will advance to the semi-finals.