Police say the victim, in his early 40s, was stabbed in a scuffle at the fast food restaurant at Eighth Avenue and West 34th Street just after 10:30 a.m.
The suspect, who witnesses said is a known homeless man from the area, first hit the security guard with his cane.
As the suspect was escorted out of the restaurant, he allegedly lunged at his victim, stabbing him in the lower body.
The bloodied guard was rushed to Bellevue Hospital with non-life threatening injuries.
The suspect fled the scene, but was caught several blocks away at Ninth Avenue and West 29th Street.