The company says the new cup will offer coffee lovers across Canada an extra large coffee at a value price.
To accommodate the new 710-millilitre cup, the names of the other cup sizes have shifted.
The original small is now extra small, the medium is now small, large is now medium and the old extra large is now large.
The company says prices won't change — guests still receive the same amount of coffee for the same price.
By comparison, Starbucks offers the 591-millilitre Venti as its largest hot coffee.
Tim Hortons spokesman Dave McKay says response to the new sizes was "overwhelmingly positive" in test marketing.
"Our guests also told us that they love our small eight-ounce (236 ml) cup, so we will continue to offer that size," McKay said.
"By shifting the sizes, we're able to provide coffee lovers with a full range of five size options," McKay added.