The Zhongxing Telecom Co (ZTE) signed a contract worth five million dollars after six months of difficult negotiations, the Xinhua news agency said on its website.
The deal was concluded in the face of what Xinhua said was "some resistance" on the part of the US-led Coalition Provisional Authority.
"On the one hand, the Iraqis themselves wished to continue working with China but on the other the Coalition Provisional Authority seemed to spare no effort in its desire to see all the contracts go to American companies," ZTE's project manager Dong Baoping was quoted as saying.
Several other Chinese companies have been to Iraq to bid for reconstruction projects, but all returned empty-handed, Xinhua said.
"On the one hand, the Iraqis themselves wished to continue working with China but on the other the Coalition Provisional Authority seemed to spare no effort in its desire to see all the contracts go to American companies"
ZTE project manager
China, one of five permanent members of the UN Security Council, opposed the war in Iraq, but was not as vocal in its opposition as France and Germany.
In December, Washington said it would exclude anti-war countries from bidding for US-funded reconstruction contracts, although it has since indicated it might reconsider.
Companies from countries opposed to the conflict have been allowed to take part in subcontracted jobs and Deputy US Secretary of State Richard Armitage said in Beijing last month the US favoured China in the reconstruction effort.
China announced last week it would soon reopen an embassy in Baghdad and has decided to write off a large chunk of the debts it is owed by Iraq.