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