A United Parcel Service worker loads orders onto a truck in the shipping area at the Overstock.com distribution center in Salt Lake City, Utah.

The investment by GSR Capital will be made at a valuation of $1.5 billion, giving the private equity firm an 18 percent stake in tZero. GSR Capital will also purchase $30 million worth of tZero security tokens from Overstock.

Overstock shares jumped as much as 21 percent in after-hours trading on Thursday after the e-commerce retailer announced that Hong Kong private-equity firm GSR Capital will invest up to $270 million into Overstock's blockchain subsidiary tZero.

The stock rose 4.47 percent during the trading day and closed at $38.60 per share.

"We are honored to have GSR Capital as a strategic investor," said tZERO CEO Saum Noursalehi in a statement. "The tokenization of securities has the potential to disrupt global capital markets responsible for moving hundreds of trillions of dollars. Together with our partners, we will globalize our blockchain-based platform, bringing more efficiency, liquidity, and trust to capital markets."

Overstock launched the tZero cryptocurrency via an initial coin offering on Dec. 18 of last year.