19-year-old Fleetwood fired a six-under-par 65 at North Berwick to win by two holes.
“The first few holes were a bit of a struggle,” said the 2008 Amateur Championship runner-up.
“Towards the end though, when I really needed it, I played well. As long as I play well, I think I’ve got a good chance of going all the way.”
Stiggy Hodgson, was assertive in his display, beating Royal Liverpool‘s Tom Boys by four holes.
Hodgson said: “You can’t get over-confident, but I feel confident enough.
“I’m striking it great and putting well, which is nice. I can’t get too excited yet, though – it’s only the first round.”
24-year-old Paisley saw off Italy’s Mattia Miloro with a three-hole victory.
The University of Tennessee graduate said: “The Walker Cup gave me lots of confidence – I had two halves in the singles there, and both were really good games. It gave me confidence that I can play on a big stage.”
Others to make it through were Welshman Rhys Enoch, Scotland’s James Byrne, Bolivia’s Sebastian MacLean, Yuki Usami of Japan and Sweden’s Henrik Norlander.