Watanabe won the Japan PGA Senior Championship in 2008 for his first senior major tournament title. Won the Fuji Film Senior Championships in two consecutive weeks and ranked second on the Japan Senior Tour Order of Merit. . .Credits Isao Aoki as his mentor in his career.
Ranked in the top 10 in his debut on the Japan Senior Tour, attracting much attention as the new money-leader. In 2009, captured the Japan Senior Open with a one-stroke victory.