Dey is a journalist, having worked for DC Thomson since 1980 and serving as sports editor of The Courier.

From 2001 to 2017, he served as MP Mike Weir's election agent, managing successful campaigns in 2001, 2005, and 2010.

[3][4] He served as Deputy Convener of the Parliament's Rural Affairs, Climate Change and Environment (RACCE) Committee during its scrutiny of the Land Reform Bill 2015.

On 27 June 2018, he was appointed as Minister for Parliamentary Business and Veterans, a junior post in Nicola Sturgeon's Scottish Government.

[7][8] In January 2022, Dey tendered his resignation as Transport Minister for health reasons.