Kammala wannan jumla: An haife shi a Glasgow, Dewar ya yi karatun Tarihi, kuma daga baya Dokar, a Jami'ar Glasgow. Kafin shiga siyasa, ya yi aiki a matsayin Lauyan a Glasgow. A lokacin da yake da shekaru 28, an zabe shi zuwa majalisar dokokin Birtaniya, wanda ke wakiltar Aberdeen ta Kudu daga 1966 zuwa 1970. Bayan ya rasa kujerarsa, ya koma shari'a har ma ya gabatar da nasa shirin tattaunawa na yammacin Juma'a a Radio Clyde. An sake zabar Dewar a zaben Glasgow Garscadden na shekarar 1978 kuma ya yi aiki a matsayin dan majalisa har zuwa mutuwarsa a shekarar 2000. Bayan nasarar da Labour ta samu a shekarar 1997, Firayim Minista Tony Blair ya nada shi Sakataren Harkokin Wajen Scotland. A matsayin sakataren Scottish, ya kasance mai ba da shawara ga Scottish devolution, kuma ya yi yakin neman zabe don majalisar Scottish a cikin
1997 Zaben raba gardama na Scotland. Bayan nasarar yakin neman zabe, Dewar ya yi aiki a kan kirkirar Dokar Scotland 1998.