But the 53-year-old, who like Hamilton is a former McLaren driver, admitted he would have advised the 2008 world champion to make a different decision as he picked a team for 2013.
"Had I been his manager then I think I would have said 'let's do a short-term deal at McLaren, for one or two years, and let's see what is out there and see who is moving'," Brundle, who used to be David Coulthard's manager, said.
"Having said that, I do think Mercedes will be much better this year and I wouldn't be at all surprised if he (Hamilton) wins a race in 2013 -- in fact, I would be surprised if he doesn't win a race because Lewis has got such speed.
"If Mercedes can harness that speed and give him the car, he will drag another quarter of a second per lap out of it somewhere and I think he'll do a great job," Brundle, now a TV commentator, told British broadcaster Sky.
"Time will tell," he said at the Autosport International show in Birmingham.