Eagles freshman Isaac Taylor scored the game-winner three minutes into the second overtime. The goal was his first of the season.
Dartmouth (10-7-1, 4-3-0 Ivy) led Boston College (13-8-0, 5-3-0 ACC) at halftime, courtesy of a one-timer from close range by co-captain Dan Keat '10 in the 30th minute, assisted by striker Lucky Mkosana '12.
Keat, in netting his eighth goal of the season, tied with Mkosana for most goals by a Big Green player this fall.
The Eagles swooped back in for an equalizer six minutes into the second half when Kyle Bekker found the net in the 51st minute.
Dartmouth dominated in regulation time, outshooting Boston 11-8, and earning nine corners, compared to the Eagles' two.
Keat and Mkosana led the team in shots with five each, and Boston goalie Justin Luthy made six saves.
Two Boston players received yellow cards in an aggressive match that saw a total of 32 fouls.
Dartmouth exits this year's NCAA Tournament two rounds earlier than it did last year, when it defeated Boston in penalties in a second-round matchup before falling to Wake Forest University 7-0 in the Sweet Sixteen.
