Kammala jumla mai zuwa: An haife shi a Flint, Michigan kuma ya kammala karatun Davison High School. Thomas ya buga wasan hockey na kwaleji don Jami'ar Vermont tsawon shekaru hudu, daga 1993-1997, a lokacin da aka zaba shi a matsayin 217th gaba ɗaya ta Quebec Nordiques a cikin
1994 NHL shigarwa daftarin. Ya buga shekaru da yawa a cikin ƙananan wasannin da Turai, kafin ya kai NHL yana da shekaru 28, tare da Boston Bruins. Daga karshe ya fito a matsayin mai tsaron gida na Bruins yana da shekaru 32. Thomas ya lashe Vezina Trophy sau biyu (2009 da 2011) a matsayin mafi kyawun mai tsaron raga na NHL, kuma ya kasance memba na Team USA a Wasannin Olympics na 2010 a Vancouver. Thomas ya lashe Conn Smythe Trophy a matsayin dan wasa mafi daraja a gasar cin kofin Stanley ta 2011. Ya kasance mafi tsufa a cikin tarihin NHL don lashe kyautar a shekara 37. Thomas yana ɗaya daga cikin 'yan wasa huɗu da aka haife su a Amurka don cin nasarar Conn Smythe Trophy, tare da Brian Leetch, Jonathan Quick, da Patrick Kane.