Towson (9-2, 5-2 in the CAA) and its high-octane offense were slowed by the Tribe's conference-best defense in the first half.
However, the Tigers seized the momentum in the second half behind gritty performances by quarterback Peter Athens and running back Terrance West (Northwestern), and withstood a furious final drive by William & Mary to emerge victorious.
"Today, we just wanted to win," West said. "It was a tough crowd, a tough place to play, they were 5-0 at home, and we came in and came up with the win."
For the majority of the game, the Tribe (7-4, 4-3), ranked No. 16 in the Football Championship Subdivision, held No. 10 Towson's offense in check before the Tigers broke through in the second half.
West was harassed early and often, but still managed to rush for 157 yards and two touchdowns while passing the 4,000-yard career rushing milestone.
While West was contained in the first half, Athens kept the chains moving for Towson at crucial times, scrambling for a handful of first downs.
Athens completed 9-of-18 passes for 94 yards and also rushed for 39 yards.
"Minus one play, I thought he was darn near perfect," Towson coach Rob Ambrose said. "He ran that offense, he controlled the tempo of the game.
"He found a way to get us yards when there weren't any yards to get, made plays, managed the clock. I could not have asked for more."
The Tigers, who averaged 40.3 points per game before Saturday, kept pounding the ball in the second half, and slowly wore down the Tribe defense.
Towson finished with 342 yards of total offense, 248 of which came on the ground.
As the Tigers' offense slowly put together a series of plays, the Towson defense halted the William & Mary rushing attack. The Tribe strung together a series of long first-half drives, but all three stalled short of the end zone, resulting in field goals.
Sophomore tailback Mikal Abdul-Saboor led the Tribe with 105 yards on 20 carries, his sixth 100-yard rushing performance of the season. Quarterback Brent Caprio and the Tribe's aerial attack were mostly silent.
"They had some good athletes, some big guys (on defense)," William & Mary coach Jimmye Laycock said. "They played hard, but I thought we played hard as well.
"We certainly played physically up front. We did a good job, but let some opportunities slip away in the red zone, fourth downs, things like that."
The Tribe jumped out to an early 3-0 lead, but Towson used a methodical 11-play, 72-yard drive capped by West's one-yard West touchdown run to take a 7-3 lead early in the second quarter.
The Tribe responded with two more field goals by John Carpenter field goals to claim a 9-7 halftime lead.
The Tigers needed a bit of trickery to score the go-ahead points. On fourth-and-9 from the 13, Towson backup quarterback Connor Frazier took the snap on a fake field-goal attempt and ran up the middle for a crucial first down.
"It obviously surprised us, but in a critical situation like that we had people there to make plays and we just didn't make plays," linebacker Luke Rhodes said. "It was disappointing, but can't control it now."
West sprinted in for a three-yard score and the Tigers converted a two-point conversion to take a 15-9 lead with 1:25 remaining in the third quarter.
Late in the game, the Tribe saw a glimmer of hope.
Towson kicker Drew Evangelista's 25 yard field goal attempt bounced off the left upright, giving William & Mary the ball with 2:42 remaining.
The Tribe got the ball to the Towson 43, setting up a crucial fourth and 10 with 1:33 remaining.
"It was fourth down, couldn't take a sack," said Caprio, whose desperation pass fell incomplete. "I tried to buy as much time as I could and throw it up and try and make a play. It just didn't work out."
For Ambrose and the Tigers, the play was eerily reminiscent of the ending between last year's game between these schools, in which the Tribe had a go-ahead touchdown pass called back because the quarterback threw the ball past the line of scrimmage.
As Caprio threw the ball Saturday, the Tigers thought he passed the line of scrimmage, and let up.
NOTES: Towson greatly improved its FCS playoff hopes with the victory. ... William & Mary's postseason hopes probably will likely hinge on next week's game against Richmond. ... Towson has won 10 consecutive road games. The Tigers' last loss away from home was against James Madison on Oct. 6, 2012. ... William & Mary saw its five- game home winning streak snapped. ... The Tribe is 3-3 this season against opponents ranked in the top 20.Copyright © 2015, The Baltimore Sun