The boy, who is not being identified because he is a juvenile, appeared at a probable cause hearing Monday. He was also charged with 17 counts of smuggling a person and causing serious bodily harm including death, and one count of evading.
The boy told investigators he drove the van because his family had been threatened, Palmview police Chief Chris Barrera said.
Barrera said prosecutors would decide whether to try the boy as an adult.
The nine killed in the rollover crash last Tuesday were all Mexican citizens. Barrera said the ground around the van was scattered with bodies.
The boy, a U.S. citizen from Hidalgo County, has cooperated with police since his arrest at home Thursday night.
"You could tell that he wanted to come clean," Barrera said.
He said the boy told them he had not done this before, but he did have a previous record.
Border Patrol agents had stopped the van in Palmview, 10 miles west of McAllen, when officials said some of the passengers immediately sprinted away and agents pursued them on foot, catching one. As the foot chase unfolded, the van sped off.
The agents came across the wreck three or four blocks away on U.S. 83. The scene was strewn with backpacks and water bottles, Border Patrol said.
ICE's investigation led to the discovery of a stash house where a dozen illegal immigrants were located. At least four of the six crash survivors were detained as material witnesses.
The teen was arrested along with six others who allegedly acted as caretakers at the stash house.
According to a complaint filed last week, two other suspects admitted after their arrests to participating in the smuggling of the illegal immigrants involved in the crash and those in the stash house. One said he was offered $40 per passenger to drive the van, but refused and instead put the 15-year-old in contact with the organization, the complaint says.
