Those arrested are in the age group of 20-25 years, police said.
The victim, a second year BSc nursing student, was raped allegedly by an autorickshaw driver and two of his friends near Ayanthi bridge in Varkala, about 50 km from here, on May 3.
A case under IPC 376 (2) (g) (gangrape) was registered against them.
The medical examination of the victim had confirmed that she had been gangraped.
The victim had gone with the autorickshaw driver, who was known to her, in his vehicle on the day of the incident.
The incident comes days after a 30-year-old Dalit law student was raped and murdered at Perumbavoor in Ernakulam district.