The Big Six energy provider said it will cut its average prices by 5.2%, which will reduce its standard domestic gas tariff by £32.
The firm, owned by German power group RWE, said the reduction will apply to around 1.2 million customers, and means that on average the annual standard npower domestic gas tariff falls to £591 per year, from £623.
The cut from npower follows similar cuts from rival Big Six providers SSE and E.On last month.
Npower RWE chief executive Paul Coffey said: "This cut in gas prices is welcome news for many of our customers.
"We have balanced the wholesale price fall against increases in the other costs we are charged."