In the programme's narrative, Jack is a time traveller and former con man from the 51st century. Abisexual, he is the first openly non-heterosexual character in the history of Doctor Who. In contrast to the wiser and older Doctor, Jack is a man of action, more willing to see the hands-on solution to the problem at hand. As a consequence of his death and resurrection in the 2005 series finale of Doctor Who, the character becomes immortal, a lasting change throughout his appearances in both series. Jack eventually becomes the leader of Torchwood, a British organisation dedicated to combating alien threats. Adding another layer to the character is a vague backstory which is gradually revealed as both programmes progress.

The popularity of the character amongst multiple demographics directly influenced the development of the spin-off series Torchwood, in which Jack is the lead amongst an ensemble cast. The character became a figure of the British public consciousness, rapidly gaining fame for portrayer John Barrowman. As an ongoing depiction of bisexuality in mainstream British television, the character became a role model for gay and bisexual young people in the UK. Jack is featured in the pages of various Doctor Who and Torchwood books, as well as having children's action figures created in his likeness from early appearances in Doctor Who.