The Aldridge-Brownhills MP becomes the first Conservative woman to hold the position, which will see her attend Cabinet and tasked with upholding party discipline.
A loyal supporter of Ms Truss, Mrs Morton worked under the new PM as a minister in the Foreign Office.
She previously served as a Transport Minister under Boris Johnson and as an assistant whip under Theresa May.
Commenting on Ms Truss's election as Tory leader, she said: "Now is the time for the whole party and country to get behind Liz’s leadership – so we can focus on tackling the serious challenges the country faces and providing the immediate support people need in the months ahead.
"I am looking forward to working with her as our new Prime Minister."
Mrs Morton is the second MP in the region to be appointed Chief Whip in recent years, after South Staffordshire MP Gavin Williamson, who held the position from July 2016 to November 2017.