Athletic director Gene Doris said a news conference would be held Wednesday at 11 a.m. on campus to introduce Johnson.
"He leads by example," Doris said, "something that is quite visible when you see the passion and enthusiasm he brings to everything he does."
Johnson, a 1997 Princeton graduate, coached at his alma mater for four years, finishing with a 66-53 record. He led the Tigers to a 25-7 record this season, including a 63-62 win over Harvard in the Ivy League tiebreaker. They ended the season with a 59-57 loss to Kentucky in the second round of the NCAA tournament.
"I think Sydney exhibits all the qualities of a successful head coach," Doris said. "He embraces the Jesuit philosophy, which is the cornerstone of Fairfield University, and exhibited a clear understanding of the University's mission during the interview process."
He replaces Ed Cooley, who left Fairfield to become coach at Providence. The Stags won a school-record 25 games this year and are expected to be a favorite to win the MAAC next season.
Before taking over at Princeton, Johnson was an assistant at Georgetown. He also was a three-time captain at Princeton, where he advanced to two NCAA tournaments. His 1995-96 Tigers upset defending national champion UCLA 43-41 in the first round.