Ian Keatley's two late penalties dug Ireland out of a hole as Joe Schmidt's experimental side edged out Fiji 23-20 in Dublin.
Joe Schmidt's men squandered a 17-3 lead built up by tries from Darren Sweetnam, Dave Kearney and Jack Conan, and almost paid the price for young fly-half Joey Carbery's two missed conversions.
Ireland made 13 changes from last weekend's record 38-3 victory over South Africa, and endured some nervy moments en route to their slender win over the eye-catching Pacific Islanders.
Henry Seniloli and Timoci Nagusa claimed tries for Fiji, with Ben Volavola slotting 10 points from the tee.
But two penalties from Munster's Keatley helped Ireland tiptoe home in a clash that will hand taskmaster boss Schmidt plenty of food for thought on his fringe stars.
Leinster playmaker Carbery's attacking prowess stood out once again, but the 22-year-old must still sharpen his goal-kicking to blossom into a long-term credible starting fly-half for boss Schmidt.
Carbery's impetuous in attacking play yielded the opening score, the young maestro stepping in to bamboozle Campese Ma'afu before floating out a fine scoring pass to Sweetnam.
Centre Jale Vatubua then unleashed a bone-shaking hit on Carbery to remind the fast-improving pivot there is more to Test rugby than simply silky skills.
Volavola's penalty had Fiji trailing just 5-3, but Ireland hit back through Kearney, who capped some considered phase play with a neat finish.
Carbery missed his second conversion, this time striking the left post, in another reminder of where he must still improve moving forward.
Only a Conway knock-on denied Kearney a second try, but Conan sealed the third score, scooping up Dominiko Waqaniburotu's dropped ball to race home.
Carbery booted the conversion as Ireland appeared in control, but in a flash Fiji countered.
Leone Nakarawa fed Nemani Nadolo on the left, and the powerhouse wing belied his frame by retrieving a deft grubber before sending Seniloli under the sticks.
Volavola's conversion cut Ireland's lead to 17-10 at the break, and Fiji drew first blood and levelled after the turnaround.
Kearney's loose pass gifted Nagusa an intercept, and the hulking wing coasted home. Volavola's conversion tied the game at 17-17.
Debutant Chris Farrell's spilled ball kick-started a flowing Fiji move, that should have ended in another score for Nagusa. But Nakarawa could not hold the wing's inside ball, letting Ireland hugely off the hook.
The scores remained locked and level for more than 20 tense minutes, before replacement fly-half Keatley edged Ireland 20-17 ahead with a penalty.
Volavola's second penalty tied the game again just three minutes later however, only for Keatley to reply in kind and leave Ireland 23-20 to the good.
Cian Healy thought he had sealed the win when bulldozing over, only to be dragged back for not releasing the ball.