Anthony Escobedo, 24, was taken to a San Antonio hospital with a collapsed lung, the television station reported.
The incident occurred in San Antonio just after 2 a.m., police said. The couple had just gone to bed when the ex-boyfriend jumped out of a closet and stabbed Escobedo several times in the back with a large knife, WOAI reported.
The woman pulled the assailant off Escobedo, police said.
The ex-boyfriend immediately fled following the stabbing, KSAT reported. There was no signs of forced entry and police know the identity of the ex-boyfriend, police said. The woman told police she had no idea how the man got into her apartment, WOAI reported.
Police are searching for the suspect, the television station reported.