In a thrilling finish and with the first-class county needing nine runs off the final over to pass the Scots' 244 for 6, Greig Williamson held his nerve to take the wickets of Steve Rhodes and Stuart Lampitt.
Lampitt, along with Gavin Haynes, had dug Worcester out of a hole after a sensational spell by the seamer Craig Wright had reduced the visitors to 98 for 5.
Wright, the man-of-the-match, claimed the two crucial scalps of Graeme Hick and Tom Moody to finish with 5 for 23. However, a seventh-wicket stand of 131 appeared to have reclaimed the initiative for Worcester until the pressure finally told.
Williamson's nerveless effort saw him induce a false shot off the second ball of the final over to have Rhodes caught by Asim Butt before Lampitt, needing to hit a six off the last delivery, lost his middle stump.
A solid century stand between Bruce Patterson and Mike Allingham earlier helped Scotland recover from the near immediate loss of Bryn Lockie, who had scored two half-centuries in a successful Benson and Hedges campaign. Patterson top scored with a studied 71, including seven fours and a straight six off Lampitt.
The all-rounder Allingham, promoted up the order, took his chance with a half-century, hitting five boundaries, and by the time he dragged on a wide delivery from Lampitt the pair's 118 stand had given Scotland a promising platform.
Essex cruised to a crushing 10-wicket victory over Cheshire as they began the defence of the trophy they won almost as easily at Lord's last September.
That day it was a nine-wicket triumph over Warwickshire with their captain, Paul Prichard, scoring 57. Yesterday, at the more homely surroundings of Chester's Broughton Hall, Prichard hit 55 to ease Essex to 96 without loss, their innings taking just 78 minutes and ending in the 24th over.
The Minor Counties side were restricted to 92, with extras making up a third of their total. They were demolished by Ronnie Irani and Peter Such, who took five wickets for 14 runs in 10 overs between them in a crucial spell after lunch.
Gary Kirsten scored 205 not out, the fourth double century of his career and his first for his country, to lead South Africa to 394 for 1 declared against British Universities at Fenner's today. He shared a 257-run unbroken second-wicket partnership with Jacques Kallis, who made an unbeaten 106 not out.Reuse content