Molinari, who is 17-under 199 for the tournament, leads Ander Hansen by one stroke and is two ahead of Marc Warren and Soren Kjeldsen, who share third place.
Mickelson continued to gain traction in the British Open tune-up. He followed up his Friday round of 64 with a 7-under 65 Saturday to pull within three strokes of Molinari. Mickelson, who opened the tournament with a 73, bogeyed the eighth hole Saturday but caught fire on the back nine at Castle Stuart Links with six birdies.
Molinari did not card any bogeys on his round; however, he played the final eight holes at even par and was unable to open up any more ground.
Alexander Noren, who shared the lead with Molinari after two rounds, shot 70 Saturday to slip back into the pack.