At 8-under-par, the 52-year-old leads by an honest three shots over Tom Kite, Ed Dougherty and Tom McGinnis at the Mississauga Golf and Country Club.
Thorpes round got started right off the bat Thursday, with a birdie at the par-4 1st. Another birdie at No. 5 gave way to a bogey at the sixth, but Thorpe responded by birdying Nos. 7, 8 and 9 for an outward half of 31.
Following four more red numbers on the backside, the big Floridian was in the clubhouse with 63, his best round of the year.
Click Here to see Jim Thorpe's scorecard.
Thorpe is coming off his finest season on the Senior circuit. He took two titles in 2000, but this year, has yet to win.
He has recorded four top-3 finishes, however, including a second at the Senior PGA Championship, where Tom Watson just edged him out.
During his career on the PGA Tour, Thorpe was a three-time winner, claiming two trophies in 1985 and another one in 86.
Full-field scores from the AT&T Canada Senior Open Championship