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 Thiruvananthapuram, on May 3.
A case under Indian Penal Code Section 376 (2)(g) (gang rape) was registered against them.
The medical examination of the victim had confirmed that she had been gang-raped.
The victim had gone with the autorickshaw driver, who was known to her, in his vehicle on the day of the incident.
Two of his friends got into the vehicle later.
They took the autorickshaw to a deserted spot and allegedly raped her, police said.
The incident comes days after a 30-year-old Dalit law student was raped and murdered at Perumbavoor in Ernakulam district.