Waterloo initially consisted of the City of Galt, the City of Waterloo, the Town of Preston, the Town of Hespeler and the Townships of North Dumfries and Waterloo.
In 1976, Waterloo—Cambridge was abolished when it was redistributed between Cambridge, Kitchener and a new Waterloo riding.
The new Waterloo riding was created from parts of Kitchener, Perth—Wilmot, Waterloo—Cambridge, and Wellington—Grey—Dufferin—Waterloo ridings. It consisted of the Townships of Wellesley, Wilmot and Woolwich, the City of Waterloo, and parts of the City of Kitchener.
In 1987, it was redefined to consist of the northern part of the City of Kitchener, the City of Waterloo, and the Township of Woolwich.