[1] He has two older sisters, Hilary and Helen, and a younger brother, Nick (born 1958) – later bass guitarist for Crowded House.

[3] In June 1980,[4] record label Missing Link[5] issued a double A-sided single "Newspaper" by the Jetsonnes and "Miniskirts in Moscow" by International Exiles.

[3][6] The Jetsonnes, Models, and International Exiles were "the first bands to rise out of Melbourne's hothouse punk, new wave explosion playing an exuberant brand of neo-pop".

[3] According to musicologist, Ian McFarlane, this was "a far more radical and unremitting concept" and Seymour, with his "blue labourer's singlet, bulging biceps, introspective angst and impassioned vocals" became the "thinking woman's sex symbol".

Seymour wrote the Hunters and Collector's song "Holy Grail", which although not intended to be about sport, has been widely used in television broadcasts of Australian Football League matches, especially the AFL Grand Final.

In September 2005, Seymour released Daytime & the Dark, an album, featuring acoustic versions of mostly Hunters and Collectors songs.

In 2013, Mark Seymour & The Undertow released Seventh Heaven Club, an album which paid homage to love songs, featuring tracks by Bob Dylan, Dave Dobbyn, Otis Redding, Neil Young, Tom Petty and Lucinda Williams.

[9] In 2023, he collaborated with synthwave group September '87, providing lyrics and lead vocals to their track Room Service.

[13] In 2008, Seymour released the memoir, Thirteen Tonne Theory, which was published by Penguin Books, detailing his experiences with Hunters and Collectors.