Emergency services were called to the West Freeway Church of Christ in White Settlement at 9.57am following reports of a shooting.
One of the victims died at the scene while another died en route to the hospital. A third victim is in a critical condition.
Macara Trusty, a spokeswoman for the MedStar Mobile Healthcare ambulance service, said all the victims were male.
No details have been released on what led to the shooting.
In an interview with Dallas TV station KTVT, Mike Drivdahl, spokesman for the Fort Worth Fire Department, said he believes the suspect was among the three who were shot.