Worcestershire 350 for 6 (Head 77, Whiteley 66*, Clarke 61, Cox 50) beat Yorkshire 346 for 9 (Pujara 101, Kohler-Cadmore 89, Barnard 3-75) by four runs
Joe Clarke, Travis Head, Ross Whiteley and Ben Cox hit half-centuries in Worcestershire's imposing 350 for six before the Rapids held their nerve with the ball to beat Yorkshire in a thriller by four runs at Emerald Headingley and continue their winning start in the Royal London one-day Cup.
Yorkshire wicketkeeper Andrew Hodd hit a six over long-on off the penultimate ball, from Charlie Morris, but needing a repeat from the final ball to rescue an unexpected victory aimed in the same direction and managed only a single.
Clarke and Head, the latter who was Yorkshire's overseas in 2016, laid the platform with 61 off 64 balls and 77 off 94. Whiteley, who hit six sixes in an over during last year's T20 Blast fixture here, and wicketkeeper Cox then put the Vikings under late pressure with 66 not out off 41 balls and 50 off 33.
They brilliantly scored the lion's share of 122 off the last 10 overs before Yorkshire started their chase strongly through ex-Pear Tom Kohler-Cadmore and Indian centurion Cheteshwar Pujara, who made 101 off 94 balls.
They took the score to 173 for one in the 30th over before sliding following the departure of opener Kohler-Cadmore for 89.
From there, Yorkshire battled hard and even took the target to six off the last ball with one wicket in hand (Andrew Hodd on strike) having been 253 for five after 42 overs. But they finished on 346 for nine.
Yorkshire conceded their second highest total in List A cricket, while Adil Rashid's two for 86 from 10 overs was his most expensive career return.
The Rapids, last season's semi-finalists, backed up Saturday's home win over Derbyshire. Yorkshire, meanwhile, have now won one and lost two.
After being inserted under overcast skies, the visitors had to navigate some early assistance for the seamers, with Daryl Mitchell trapped lbw by Ben Coad - 14 for one.
Clarke and Australian Head then shared 108 in 17 overs for the second wicket before the innings slowed up somewhat as they fell to 220 for five in the 39th, losing Clarke run out backing up and Head superbly caught and bowled by Rashid.
But Whiteley strengthened an excellent recent limited overs record against Yorkshire with some blistering hitting, while Cox was equally dynamic.
The runs then continued to flow at the start of the Yorkshire reply.
Openers Kohler-Cadmore and Adam Lyth shared 72 inside 12 overs before Pujara joined the former to share 101 in 18 overs for the second wicket.
While Kohler-Cadmore added to last Friday's 164 in beating Durham, Pujara passed 50 for the third successive innings.
But the chase faltered in the 30th over when leg-spinning all-rounder Brett D'Oliveira returned and had Kohler-Cadmore caught at long-on and pinch-hitter James Wainman caught behind in three balls.
Yorkshire quickly slipped from 173 for one and reached 40 overs at 240 for four.
Pujara reached his hundred shortly afterwards, but it was all but game up when he found deep mid-wicket off Ed Barnard's seamers.
Some exhilarating lower order hitting raised home hopes again, but it was to no avail as 16 off the last, and then six off the last ball, with one wicket left was a step too far.