"Let's keep building this culture and making a difference," Moser wrote in a statement. "Let's keep chasing championships."
Moser led the Ramblers to a 32-6 season and the Final Four in 2017-'18. Loyola went 20-14 and won the Missouri Valley Conference regular-season title this past season but failed to land an NCAA Tournament bid, as it lost in the conference tournament.
Moser is 141-125 (.530) in eight years at Loyola.
St. John's has offered an eight-year deal worth around $2.2 million annually, according to reports.