The money-saving move will mean all 18,000 staff at its 24 offices will only use their mobiles for business calls.
The company claimed mobiles would be “more efficient”, though it did not reveal the expected savings.
It said: “We already equip our people with a mobile and many had already moved away from using their landlines.
“With landline usage falling rapidly a mobile-focused policy is more efficient.”
The firm added that a few landlines would remain – for security personnel to use, in rooms for client meetings and for use at reception.
But it said meeting rooms will use “conferencing technology” linked to mobiles.
Many small businesses have abandoned landlines in favour of mobiles in recent years, but PwC is one of the first large firms to do so.
The move comes amid a sharp fall in landline use among businesses.
In 2010, businesses in the UK had 10 million landline numbers.
That had fallen to 6.4 million by the end of last year, according to Ofcom.
The amount of time businesses spent talking on landlines has dropped even more.
In 2010, businesses logged almost 38 million minutes of calls, but that had halved to 18.8 million in 2017.
Residential use of landlines is also down.
In 2010 UK households made more than 90 million minutes of phone calls, but that had fallen to 35 million minutes by last year.
However, most homes need a landline for broadband, so the number of residential lines has risen since 2010.
James Barford, telecoms analyst at Enders, explained: “Because of the pricing structure most people have to have a landline to get broadband.
“But younger people often don’t even plug in a handset.”
BT was forced to cut the cost of a landline by £7 a month for customers that only had a landline, this year.