Parsons rattled in ten birdies against no bogies and leads by two strokes over Welshman David Park, who carded an opening-day 64.
Until this day, the Australian had been having a tough time on the European Tour.
While he won the 00 Greg Norman Holden International, it has been relatively downhill since, with the 32-year-old making only seven cuts in his 20 appearances in 2001.
However, a recent trip home to Australia and a visit to his swing coach seems to have done the trick.
I went home four weeks ago to see my coach Barry Bent, and found I was doing something for six months I wasnt even aware of, claimed Parsons.
It was a small technical thing, he explained. It took me 24 hours to get out there (Australia), 24 hours to get back, and about an hour to fix!
He certainly had it fixed on Thursday, canning nearly all his birdie putts from inside of ten-feet, with the lone exception a 25-footer on the fifth.
Said Parsons: I was hitting it both ways, but I feel I have the ball under control now.
The Cannes Open is in its first year back to the European Tour following a three-year absence from the schedule. The first-place prize this week is slightly over $84,000.
Click Here for Full-Field Scores from the Cannes Open.