A 140-year-old firm, which sells everything from vacuum cleaners to nuclear reactors, posted a net loss of 12.27 billion yen in the three months to June.
Sales fell 4.5 per cent from a year earlier to 1.35 trillion yen, the lowest since the quarter ended December 2012, due to a poor performance in television and personal computer businesses.
Toshiba said in a stock exchange filing its electric and nuclear generation businesses also saw a weak three months.
The net loss was a reversal from a previously expected 120 billion yen annual profit.
One of the most damaging accounting scandals to hit Japan in recent years, the case forced the incumbent president and seven other top executives to resign after a company-hired panel found top management colluded to puff up profits.
The embarrassing findings came as Japan adopted a long- awaited corporate governance code aimed at improving firms' transparency.