It was still unclear during an arraignment Monday how Yordi Barthelemy, who is the 23-year-old accused of their murders, is related to the victims.
Barthelemy, of Kerns, Texas, was given no bond for his capital murder charge. He was also charged with assault-family violence in connection to the killings.
Officers were called to a "family disturbance" at a condominium in the island city about 10 p.m. Saturday and arrived to find the women shot dead, police said in a statement.
Police said the suspect fled the scene of the shooting but later turned himself in and was arrested in the neighboring community of Port Isabel.
The victims were 46, 47 and 65 years old and from the Houston area, police said.
Police did not provide the women's names or did not immediately answer questions about a motive in the shootings.
Barthelemy is expected to be booked into Cameron County jail at a later date.
South Padre Island is a community on a barrier island of the same name, off the southern coast of Texas near the Mexican border.
The Associated Press contributed to this report.