Ma Dai was a younger cousin of Ma Chao. He does not have a biography in the "Records of the Three Kingdoms" ("Sanguozhi"), the authoritative source for the history of the Three Kingdoms period; he is mentioned occasionally in the biographies of other people such as Ma Chao and Wei Yan. He is first mentioned in Ma Chao's biography in a letter written by Ma Chao to Liu Bei before his death. Ma Chao wrote: "Over 200 members of my family were killed by Cao Cao. I only have my cousin Ma Dai left with me. He will be the one to continue my family line. I entrust him to Your Majesty's care. That is all I have to say." Ma Dai served in the state of Shu Han as a military general. The highest position he attained was "General Who Pacifies the North" (平北將軍). He was also enfeoffed as the "Marquis of Chencang" (陳倉侯).