The energy firm said electricity prices will rise by 9.3% and gas prices by 11.1% from December 1, meaning the average dual fuel customer's bill will rise by £137, or 10.4%, a year, from £1323 to £1459.
Npower, which has almost 130,000 customers in Scotland, is the third of the "Big Six"energy firms to announce price hikes. It raised tariffs by 8.9% last year.
Mark Todd, director of price comparison service energy-helpline, said yesterday he now expects ScottishPower, EDF and E.ON UK to follow suit and raise their own prices in line with other companies' tariffs.
British Gas recently announced it is hiking the cost of electricity by 10.4% and gas by 8.4% - affecting 7.8 million households - while SSE said it is hitting seven million customers with an 8.2% rise.
Mr Todd said: "This is devastating news and is proof to cash-strapped consumers that customer loyalty reaps no benefits.
"The truth is that there is nowhere to hide from the energy hikes and more suppliers are set to follow suit."
The npower price rise in Scotland will depend on where customers live, with higher charges for those in the north of the country due to the cost of transmitting electricity across wide distances.
A spokeswoman for the company said: "Depending on the area of Scotland npower customers are in, the average dual fuel increase will be between 10.5% and 10.3%.
"This is because we have to pay different costs to the distribution network owners, depending on what area we're supplying to.
"Customers living in the 'Scottish-Hydro' distribution zone will see an average dual fuel increase of 10.3%, whereas customers living in the 'Scottish-Power' distribution zone will see dual fuel prices rise by 10.5%."
Npower's announcement follows Labour leader Ed Miliband's pledge to freeze energy prices for 20 months if his party wins the next election, and is likely to intensify the debate over the soaring cost of living.
But RWE npower chief executive Paul Massara said a bill freeze would not lead to lower sustainable prices because it would not cut the cost of supplying energy.
He added that the German group only aims to make a profit of around 5p in the pound.
He said: "Only 16% of the bill is under our control and imposing price controls discourages investment, increases uncertainty and ultimately leads to higher prices."
Deputy First Minister Nicola Sturgeon said the Scottish Government would cut fuel bills by 5% if there is a Yes vote in the upcoming independence referendum.
But MP Tom Greatrex, Scottish Labour's Shadow Energy Minister, dismissed the plan as a "sleight of hand", claiming the cut would be paid for out of people's taxes.
He said: "Scots struggling with the worst cost of living crisis in a century will be shocked by npower's decision to hike prices by more than 10%.
"We are all paying the price as David Cameron and Alex Salmond fail to stand up to the big energy companies."