The Spartans compete in 28 National Collegiate Athletic Association (NCAA) Division III intercollegiate sports.

Castleton's men's soccer team were declared 1963 NAIA co-champions (along with Earlham College of Indiana) after the championship and consolation games at Frostburg State University in Maryland were cancelled due to snow.

Beginning in 2025-26, the Spartans will join the Little East Conference for Ice Hockey, departing the NEHC.

The Castleton Spartans football team represents the school in NCAA Division III.

[14] It has been part of the Eastern Collegiate Football Conference (ECFC) since its inaugural season in 2009.