It happened around 7 p.m. at Creekside Off-Road Ranch in Splendora.
Authorities said they initially received a call regarding a "rescue and entrapment" at the park. Investigators had a hard time locating the child due to the darkness and terrain in the area. They were finally able to locate the ATV in the back portion of the park.
The 4-year-old, who has not been identified, was found non-responsive.
It's unclear how the crash occurred. The incident remains under investigation.
Earlier this month, a 4-year-old boy was hospitalized after he was severely injured during an ATV accident in Katy.
READ MORE: 4-year-old boy injured during ATV accident in Katy
4-year-old boy injured in ATV accident in Katy