Ireland have topped the world rankings for the first time with a 19-10 victory in Dublin.
Fly-half Patchell was bulldozed by flanker CJ Stander in the build-up to the game's first try, as boss Joe Schmidt toasted his final match at the Aviva Stadium by steering Ireland to the top of World Rugby's rankings.
Ireland were left to sweat a possible knee injury for wing Keith Earls, amid a confidence-boosting victory where Kearney, Tadhg Furlong and James Ryan all bagged tries.
Head coach Schmidt and captain Rory Best will relinquish their roles after the World Cup, and both claimed the Aviva Stadium sign-off they so craved.
MATCH IN 60 SECONDS
Having trailed 10-7 at half-time, Ireland started the second period with intent with two tries before the hour mark, both forward-powered as Tadhg Furlong and James Ryan drove over the line to establish a decisive lead.
Ireland signed off for Japan on a winning note and the number one side in the world rankings after they defeated Grand Slam champions Wales in a competitive contest that bodes well for the World Cup opening pool game against Scotland on September 22. It also gave captain Rory Best and head coach Joe Schmidt a good memory or two to cap their last home games before they step away from the Ireland team at the end of the World Cup.
James Ryan grabbed the decisive try on 59 minutes to cap a typically industrious and effective performance in the Ireland engine room as his team took another step in the right direction towards hitting their straps in Japan later this month.
French official Mathieu Raynal was a steady presence in the middle with little in the way of controversy to deal with. There was also a great moment of sportsmanship as Hadleigh Parkes went over the Irish line in the first half and was turned skyward by tackler Robbie Henshaw, Wales fly-half Dan Biggar telling the referee “No try, held up”.
Ireland 6 Wales 12 + 3 f-k
Keith Earls’s first game of the summer ended prematurely when he was withdrawn in the second half, Joe Schmidt describing his injury as bang on his quad muscle, just above the knee, while the boss was confident Cian Healy was well having not returned from a half-time Head Injury Assessment.
So the phoney war comes to an end and the real fun begins. Ireland’s 2019 World Cup squad departs for Tokyo on Wednesday and onto a training base in Chiba ahead of their Pool A opener against Scotland in Yokohama on Sunday, September 22.
R Kearney; J Larmour, R Henshaw, B Aki, K Earls (G Ringrose, 52); J Sexton (J Carty, 63), C Murray (L McGrath, 72); C Healy (D Kilcoyne, h-t - HIA), R Best - Captain (S Cronin, 52), T Furlong (A Porter, 56); J Ryan, J Kleyn (I Henderson, 52); CJ Stander, J van der Flier (R Ruddock, 59), J Conan.
L Halfpenny (L Williams, 66); G North, J Davies, H Parkes, J Adams; R Patchell (D Biggar, 23), T Williams (G Davies, 69) ; W Jones (N Smith, 59), E Dee (K Owens, 59), T Francis (D Lewis, 59), J Ball (A Beard, 74), A W Jones - captain, A Wainwright, J Tipuric, R Moriarty (J Navidi, 59).
Beard - 73mins
Mathieu Raynal (France)
More from the match: Powering through Wales' midfield
Ireland wobbled at the lineout again from the off, Joe Schmidt's side still getting to grips with the absence of set-piece banker Devin Toner.
Brian O'Driscoll this week insisted omitting Toner from Ireland's World Cup squad "beggars belief", and early on here the lineout jitters certainly backed that stance.
Captain Rory Best and locks James Ryan and Jean Kleyn warmed to their set-piece task however, with one penalty lineout laying the platform for the game's first score.
Bundee Aki and Stander powered through Wales' midfield, with the latter clattering Patchell and ending the fly-half's afternoon prematurely. That quick ball allowed Kearney to ghost past Jonathan Davies and across the whitewash, with a sharp-looking Johnny Sexton posting a smart conversion.
Biggar snatched an interception pass off Sexton to race towards the line, only for Henshaw to haul back the replacement fly-half and deny him a score.
Wales kept up the pressure however, with Hadleigh Parkes busting home in style and Leigh Halfpenny's conversion handing the visitors a 10-7 lead at the break.
Ireland built their fluency after the break though, Conor Murray and Sexton running the show in what will prove a huge relief to boss Schmidt.
Tighthead prop Furlong powered home to wrestle the lead back into Irish hands and then lock Ryan busted in too.
Jack Carty replaced Sexton just past the hour, with Ireland's premier playmaker withdrawn safe and sound - to be bubble-wrapped en route to Japan such is his importance to Schmidt's side.
Scrum-half Murray negotiated the encounter unscathed too, which will relieve the Irish public just as much as boss Schmidt.
Adam Beard was sin-binned at the death for Wales, paying the price for the visitors' repeated infringement, before Ireland closed out their spirited win.