Health officials say all four cases are among unvaccinated members of the same family.
The Montgomery County Hospital District tells ABC13 that these are the county's first measles cases since 2019.
Dr. Casey Patrick, who is the medical director for the Montgomery County Hospital District, says their message to the community is about the importance of prevention through vaccines.
"Everything in life is a risk-benefit choice," Patrick said. "The choice to vaccinate is infinitely less risky than actually having measles."
Patrick said the measles are highly contagious and transmitted through respiratory droplets.
He said early symptoms include a cough, runny nose, and pink eye before a rash develops.
Meghna Joshi, who is also with the Montgomery Hospital District as its epidemiology and preparedness manager, says they're currently working on meeting with area school districts.
She said it's a practice they do each year.
"We have to get them up-to-date and up to speed on what's happening in Montgomery County in order for them to prepare and know what to do for their students and their staff," Joshi said.
She said they'll be going over signs and symptoms with the districts and encouraging them to review their school's vaccination rates as it relates to these measles cases.
The ABC News Data Team reviewed vaccination rates among kindergartners in Texas and found that Montgomery and Harris Counties are traditionally a little bit behind the rest of the state.
They found that 92.9% of Harris County kindergartners were vaccinated against measles in the most recent school year.
It was at 92.1% in Montgomery County during the same time period.
The overall number in Texas among vaccinated kindergartners was 93.3% in the 2025-2026 school year.