A spokeswoman for Dow Jones, the newspaper's publisher, said the Journal has completed a network overhaul to bolster security.
The New York Times also reported that Chinese hackers repeatedly penetrated its computer systems and stole reporters' passwords. The newspaper said the hackers were hunting for files on an investigation into wealth amassed by the family of a top Chinese leader.
The Journal did not address how the hacking of its systems occurred, but it said it has faced such threats from China in recent years. It said the hacking was not an attempt to "gain commercial advantage or to misappropriate customer information".