They will join Paolo Nutini and Rita Ora who have already been confirmed to play at the annual free BBC event which is taking place on Glasgow Green on 24 & 25 May.
Tickets will be given away from from 8am on Monday 31 March, with 25,000 available for each day.
Organisers said Pharrell will perform on the Saturday, while The 1975 will play on the Sunday.
Pharrell said: “I am so excited and honoured to be playing Radio 1’s Big Weekend. Over the years I’ve been in awe of the amazing world-class talent at the event and to know that I will be a part of it this year is so humbling. Can’t wait to see you guys!”
Radio 1 Breakfast Show host Nick Grimshaw revealed the additions to the line-up on his programme today.
Top DJs Annie Mac, Pete Tong, Zane Lowe and others will take over Glasgow’s George Square for the Friday curtain-raiser before the weekend event.
Tickets will be available online at Radio 1’s website and by calling 0844 858 9071.
The full line-up and headline artists to perform at the event, now in its 11th year, will be revealed on Radio 1 next month.