That victory was less than one year into his career in 1993 when he captured a European secondary Challenge Tour event near Euro Disney in France.
Since then Mickelson has claimed four Major Championships and 40 other titles including 33 regular PGA Tour events.
"Boy, that was 20 years ago and I don't really remember much about the week other than I went to Euro Disney and had a good time," he said.
"I played Steve Elkington in the finals and we went head-to-head.
"I was quite a few back and shot a low final round to clip him by one or two."
Mickelson is competing in his ninth Scottish Open and at No. 8 in the world is the highest ranked player teeing up on the Gil Hanse designed Castle Stuart course.
Castle Stuart is hosting the event for a third straight year before the event heads east next year to Royal Aberdeen and Mickelson is hoping to draw on the fact the last two Open Championship winners in Darren Clarke and Ernie Els each competed in Inverness the week prior.
"The last eight years I've started to play better on links-style courses, better golf in bad weather and better golf along the ground," he said.
"But it's still a challenge for me and it's still not something that I grew up learning but it's something I am still trying to learn as I continue through my career.
"So I am always cautiously optimistic.
"The British Open, the Open Championship, it's one of my favourite events because it's one of the most challenging events for me.
"But then Castle Stuart is a great place to play in the week prior the British Open.
"It's just a wonderful golf course, and gives me a chance to work on shots along the ground, short game, putting while the grasses are very similar."
And as Mickelson also looks to become the first American-born winner of the Scottish Open since Tom Lehman in 1997, he revealed he has five different putting greens in his Californian residence.
"Golf is different than basketball as we don't play on the same hard court every week, so I have different putting greens," he said.
"I have a beet green, I have a poa annua green, I have a MiniVerde green, I have a Bermuda, and so I have different surfaces to practice on and get ready for up-coming tournaments."