The stock had climbed more than 10 percent, or $1.97, to $20.97 from its IPO price in midday trading while broader indexes rose slightly.
JD.com Inc. had offered about 69 million shares in the IPO, while selling shareholders offered 24.7 million. The company's stock was priced at $19 per share, or a dollar higher than the range it had forecast.
The company says it plans to use some of the offering's proceeds to build new warehouses and buy vehicles for shipping and delivery.
JD.com's larger rival in China, Alibaba, also plans to debut on American stock markets. Its shares have not started trading.