The robberies date back to December 2020.
In the most recent case, which unfolded on Aug. 3 at around 11:35 p.m., police say a woman was taking out cash from an ATM in the 11600 block of Westheimer Road.
She said a man suddenly appeared with a gun and asked for her money. Police say the woman drove off and left the man standing in front of the ATM with her account information still accessible.
The suspect got away with $400, according to investigators.
All of the robberies happened at ATMs along Westheimer Road in west Houston, just past the Beltway.
At one point, according to police, the suspect hit two different ATMs on the same day.
Investigators believe the suspect lives in the area.
He's being described as a Black man in his late 20s who's about 6 feet tall. Investigators say he has a darker complexion with a slim build and has short dreadlocks with gold or brown tips.
Anyone with information on any of the nine robberies is urged to contact Houston police.
READ ALSO: Exclusive video shows frightening moments Sugar Land mom gets robbed: 'My baby's in there!'
Video shows frightening moments Sugar Land mom gets robbed
For updates on this report, follow ABC13 reporter Erica Simon on Facebook, Twitter and Instagram.