Poundland has agreed to a £597 million takeover by South African firm Steinhoff International.
The firm, which already holds a 23% stake in Poundland, will pay 222p per share for the rest of the business.
Poundland chairman Darren Shapland said: "The Poundland board believes that Steinhoff's all-cash offer presents Poundland shareholders with an opportunity to realise their shareholding at a certain and attractive price."
The South African retail company submitted an informal offer in June, but that was rejected.
Poundland bought the 99p Store in September last year, and has since seen its shares fall by more than 50% as sales growth slowed down. In February 2015, it had been trading at 418p, but has fallen as low as 150p since. Following the announcement of the takeover, Poundland's shares jump more than 12% to 220p per share.