Tennant will appear in the first episode of the surreal sketch show, playing the role of the outrageously camp Mr Slightlyman.
A wedding planner with a passion for plastic surgery, Mr Slightlyman is a local celebrity on the island of Jinsy and has the nickname 'Master of the Balls' because of his role as boss of the marriage lottery.
Catherine Tate, Simon Callow and Jennifer Saunders have also signed up for cameos later in the series. Last week, pictures of Harry Hill's character in the programme, Joon Boolay, were unveiled.
This Is Jinsy, which is created by and stars newcomers Chris Bran and Justin Chubb, will air on Sky Atlantic in September.
Watch a trailer for This Is Jinsy below: