Okada entered Nintendo in 1975, and went on to work as an engineer at Nintendo Research & Development 1 with Gunpei Yokoi, who developed the hugely successful Game & Watch and Game Boy handheld game consoles. In 1996, Yokoi left Nintendo which caused R&D1 to split, its engineers creating a portable hardware division of which Okada became the general manager. His team lacked Yokoi but nevertheless developed hugely successful handheld consoles, those being the Game Boy Color, Game Boy Advance and Game Boy Advance SP and most recently the Nintendo DS.
Okada also participated in the development of several Nintendo games, as the chief director of Metroid, director of Kid Icarus, Solar Striker (along with Keisuke Terasaki) and Super Mario Land and contributor to many other titles. Nowadays, he is fully dedicated to designing and developing handheld consoles.