After a night of close calls at both ends, Norwich captain Holt had the easiest of tasks in the 89th minute when the ball fell to him a few yards from goal, after Hoops keeper Fraser Forster had blocked a drive from Jonathan Howson, to slam the ball into the net.
Brighton heaped more misery on crisis club Portsmouth with a 5-1 friendly win.
Gus Poyet's side opened the scoring in the 11th minute when Will Hoskins raced onto Vicente's pass and found the corner, while the Spaniard then set up a goal for Matt Sparrow (23), who fired home from 20-yards.
Vicente (35) was running riot and he surged towards the box before blasting into the top corner, but Pompey did pull one back when Dan Thompson (45) turned the ball home from close range.
Brighton quickly responded after the break as the masterful Vicente whipped in a free-kick which was nodded home by Romain Vincelot (48).
And young striker Torbjorn Agdestein completed the scoring in the 62nd minute when he turned in Hoskins' low cross.
Burnley claimed a 1-0 win over Bury in a pre-season friendly at Gigg Lane thanks to Danny Ings' late strike.
There were plenty of chances for both sides in an open match but it took until the 81st minute for Ings to settle the contest.
The forward burst onto Keith Treacy's through-ball and kept his cool to slot past advancing Shakers goalkeeper Trevor Carson.