Wigan Athletic confirm triple capture
Clough and Whelan join Latics following their spells with Nottingham Forest and Phoenix Rising, respectively.
Scotland youth international defender Johnston - who, like Whelan, came through the ranks at Liverpool - has signed on loan from Dutch side Feyenoord.
The signings of Whelan and Johnston are subject to international clearance.
Clough will wear the No.7 shirt, Whelan No.6 and Johnston No.5.
Get 20% off our sports subscription package and stay up to date with all the latest Wigan Athletic news with a year’s subscription to WiganToday for less than 9p a day. Use promo code TRANSFER20