Sebastian will be featured across marketing communications and promotions for the new service, which had a soft launch last month.
Foxtel Play packages offer a selection of Pay TV channels through an internet subscription, along with Foxtel GO tablet and smartphone viewing.
Guy Sebastian said: “It’s a thrill to join such a progressive and dynamic media company like Foxtel. This is an exciting time of our lives as habits change and access to entertainment expands. Foxtel Play is a brilliant example of what a game changer this new service is.”