Following her service as District Attorney of Middlesex County, Coakley was elected Attorney General of Massachusetts.
After completing her undergraduate education at Williams College, she received her law degree from Boston University and subsequently worked for the Boston-based law firms Goodwin Procter and Parker, Coulter, Daley & White.
In the late 1990s, she was one of the lead prosecutors in the trial of British nanny Louise Woodward for the wrongful death of Matthew Eappen, the Massachusetts-born infant who had been in her care.
She grew up in North Adams, Massachusetts, as the daughter of Phyllis and Edward Coakley. She later settled in Medford, Massachusetts, with her husband Thomas O'Connor.
She lost the 2010 special U.S. Senate election (to replace the recently deceased Ted Kennedy) to Republican candidate Scott Brown.