The highly promising youngster made nine birdies and a single bogey for his 64 at Aloha Golf Club to finish on eight under par and move three strokes clear of his nearest rivals, Swede Niclas Fasth, English duo Anthony Wall and qualifying school graduate Lloyd Kennedy, South African Open champion Hennie Otto and local player Eduardo de la Riva.
Spain seems to be a happy hunting ground for Manassero - the first of his two European tour victories came at the Castello Masters in 2010.
"This is quite similar to Castellon - a little bit more hilly maybe," he said.
"It's my first time at Aloha. This course suits my game because it's not long, and I don't need to hit 300 yards to reach the par fives. You need accurate shots and a good strategy, and I enjoy this type of course.