The deal makes state-owned Unicom the first Chinese phone company to formally support the device, however several unlocked iPhones are widely used.
"We believe China Unicom's high-speed mobile broadband network, coupled with [the iPhone] will create new communication and different experiences for customers in China," Unicom chairman Chang Xiaobin said in a report.
Xiaobin also said the company would not share revenue with Apple but instead would buy phones in batches and offer them with subsidies.
With approximately 650 million mobile phone accounts, China is among the world’s biggest cell phone markets, according to reports.
Unicom claims it has 133 million accounts last year; the addition of the iPhone may help it compete with China’s dominating service provider — which says it has more than 450 million subscribers.