Ishii played for the Japanese national baseball team at the 1988 Summer Olympics and the 1988 Baseball World Cup. He led all pitchers in the 1988 Cup in strikeouts (32 in 27-1/3 IP), beating out the likes of Andy Benes, Ben McDonald, Charles Nagy, Jim Abbott, Hideo Nomo and Orlando Hernández. Ishii went 3–0 with a save and a 0.99 ERA. He allowed only two walks and 15 hits. He joined Abbott as the tourney's All-Star pitchers. He tried to save the semifinals after Hideo Nomo faltered in the 8th but allowed a single, triple, and a balk without retiring anyone in the loss to Cuba that eliminated Japan.