Kōtarō Isaka was born in Matsudo, Japan. He studied law at Tohoku University, after which he was worked as a systems engineer. In 2000, he won the Shincho Mystery Club Prize for his first novel. Soon after, he committed himself to writing full-time.
His novel Jūryoku Piero (2003), for which he won the Naoki Award, made him famous. His books have sold millions of copies worldwide.
Kōtarō Isaka is often referred to as a crime writer, but he dislikes this definition for being too restrictive. This won him many fans from the younger generation.
His 2010 novel Bullet Train was made into a movie in 2022, starring Brad Pitt. The book was also translated into Polish.