The Terps were dominant all game, holding the Blue Devils to a season-low five goals.
The two connected three times in the final 25 minutes to send the Terps through to the NCAA semifinals against Duke.
DeMaio needed just 39 seconds of overtime to claim a victory for the Terps and set a date with Duke in the semifinals.
Jared Bernhardt led the way, scoring six goals for the Terps, earning a first round victory over the Catamounts.
The Terps are set to face Vermont in the first round of the tournament on May 16.
The Terps relied on five different goalscorers in the second half to earn their third Big Ten title.
Three late goals helped the Terps beat their rivals and clinch their third Big Ten championship.
Bernhardt's career-high eight goals and 10 points helped him become the Terps' all-time leading points scorer.
The Terps play Thursday against Michigan.
Jared Bernhardt and Nick Grill were named the conference's offensive and defensive player of the year, respectively.