Mizuho Securities Co., Ltd. (みずほ証券株式会社, Mizuho Shōken Kabushiki-gaisha?) is a Japanese investment banking and securities firm. It is a subsidiary of Mizuho Corporate Bank, Ltd., which is a wholly owned subsidiary of Mizuho Financial Group, the second-biggest Japanese financial services conglomerate.
The current Mizuho Securities is established by a merger between Shinko Securities and the former Mizuho Securities. The former Shinko Securities (a former equity-method affiliate of Mizuho Financial Group) and the former Mizuho Securities (a former consolidated subsidiary of Mizuho Financial Group) merged on 7 May 2009. The surviving entity was the former Shinko Securities, which changed its name to Mizuho Securities upon the merger. After the merger, Mizuho Financial Group holds 59.51% equity ownership of the new Mizuho Securities.
On 8 December 2005, Mizuho Securities erroneously placed an order to sell 610,000 shares of J-COM Co., Ltd. for one yen each, instead of a commissioned order to sell one share of J-COM Co., Ltd. for 610,000 yen at Tokyo Stock Exchange. J-COM Co., Ltd. (J-COM Holdings Co., Ltd. since December 2009) is a Japanese staffing service company, which was listed on the Mothers (Market of the high-growth and emerging stocks) section of Tokyo Stock Exchange on the day. As a result of this incident, Mizuho Securities accrued a loss of approximately 40.7 billion yen.