The 51-year-old Andrade had eight birdies — three in a row on Nos. 13-15 — and a bogey to reach 10-under 134. The four-time PGA Tour winner teamed with Joe Duran to win the Legends of Golf in April for his first Champions Tour title.
Bernhard Langer, who won the Boeing Classic in 2010, and Jeff Freeman were tied for second. Langer had a 66, and Freeman shot 68. Fred Couples, from Seattle, was tied for fourth at 4-under after a 71.
Final round action is Sunday at TPC Snoqualmie Ridge.