Daboll replaces former Giants head coach Joe Judge, who posted a 10-23 record and was fired after two seasons. Judge became the third straight Giants coach to be fired after two seasons or less.
"I have a pretty good idea where our fan base's feelings are right now, and I get it," Daboll said in a statement. "I promise we will work our tails off to put a team on the field that you will be proud to support and give us the results we all want."
Daboll was one of five finalists for the Giants' head-coaching job. Former Miami Dolphins coach Brian Flores, Bills defensive coordinator Leslie Frazier, Dallas Cowboys defensive coordinator Dan Quinn and Giants defensive coordinator Patrick Graham also were considered for the position.
The 46-year-old Daboll spent the past four seasons as the Bills' offensive coordinator. He guided top-five offenses in Buffalo each of the last two years, and he is credited with the development of star quarterback Josh Allen.
Daboll joins former Bills assistant general manager Joe Schoen in New York. After the retirement of Giants general manager Dave Gettleman following the conclusion of the season, Schoen was hired in his place.
"Over the last four years, I have observed first-hand Brian's strengths as a leader -- he is an excellent communicator, intelligent, innovative, and hard working," Schoen said in a news release. "Brian's genuine and engaging personality is refreshing. He fosters relationships with the players and coaches around him.
"He is progressive in his vision and values collaboration, two of the attributes we think are essential. I am thrilled to partner with Brian and welcome he and his family to this side of the state."
Under Schoen and Daboll, the Giants will look to develop young quarterback Daniel Jones and return to postseason contention. New York hasn't reached the playoffs since 2016, and the franchise has failed to win a postseason game since its Super Bowl title in 2011.