On 20 May 2007, Ishikawa became the youngest winner ever of a men's regular tournament on the Japan Golf Tour by winning[2] the Munsingwear Open KSB Cup at the age 15 years and 8 months.

[4] Ishikawa turned professional in 2008[5] and won another Japan Golf Tour tournament, the mynavi ABC Championship.

[6] Ishikawa dominated the Japan Golf Tour for much of the 2009 season and was the top-ranked Japanese player in the World Rankings.

[9] On 30 March 2011 Ishikawa announced that he would be donating all of his 2011 tour earnings, plus an additional ¥100,000 for every birdie he made during the year, to the Japan earthquake relief efforts.

[12] He made 13 cuts in 23 events, finishing 149th on the money list and missing the FedEx Cup playoffs (ranked 141st).

Ishikawa had nine top-25s and made 14 cuts during the 2014 season, including a second-place finish at the Shriners Hospitals for Children Open and a tie for fifth at the unofficial ISPS Handa World Cup of Golf.

1Cancelled due to COVID-19 pandemic QF, R16, R32, R64 = Round in which player lost in match play NT = no tournament "T" = tied Professional