The spectacular event, which tells a story based on the Titanic tragedy, will see three giants travel more than 20 miles through the city centre from April 20 to 22.
Organisers had already announced the show would star the 30ft Little Girl and the 50ft Uncle and now the team have announced a 9ft dog Xolo, the Little Girl Giant's best friend.
The latest addition is 3.5metres long, weighs 200 pounds and can reach speeds of up to 6kph.
Liverpool City Council's Cabinet Member for Culture and Tourism, Councillor Wendy Simon, said: "When we originally announced that the Little Girl Giant was coming to the city there was a huge amount of excitement, and now we have three giants exploring Liverpool this has turned out to be the must-see event of the year!
"Xolo will add a fantastic dynamic to the show - he's fast, playful and fantastic to watch - it won't just be dog-lovers he'll appeal to but people old and young.
"This is the first time street theatre experts Royal de Luxe have ever brought three giants to the UK, so it's a real coup they want to showcase some of their most popular characters in our city.
"It really will be an unmissable event, and one that people will remember for years to come."