Tsuyoshi Kikukawa, the former Olympus chairman, has pleaded guilty to charges of falsifying accounts and covering up losses of $1.7bn, in a trial that begins on Tuesday.
Kikukawa, along with two other former executives, as well as the company itself, filed a guilty plea in Tokyo District Court.
A former former chief executive, Michael Woodford, brought to light the financial irregularities by the three men who were hiding the losses.
"There is no mistake. The entire responsibility lies with me," Kikukawa said in the court.
The scandal was revealed when Woodford, the British chief executive, was dismissed from his post last year after he challenged Kikukawa and the board over suspiciously large payments related to acquisitions.
Kikukawa, former executive vice president Hisashi Mori and former auditing officer Hideo Yamada, were arrested in February and later indicted on suspected violation of the Financial Instruments and Exchange Act.
They could face as much as 10 years in jail.