William Berrioz, 23, entered the plea in court on Thursday morning. Sentencing is scheduled for June 16th.
Berrioz, of the1300 block of North Dover Street, was charged in the attack back in January.
Police say he stabbed 64-year-old Ben Davis of Camden six times with an 8 1/2 inch long knife. Davis survived the attack
Investigators also say Berrioz punched and stomped a security guard who helped catch him after the stabbing at the Mellon Independence Center, formerly known as the Lit Brothers Building.
Police say Davis and his wife were at a hair salon for a regular appointment. Davis would usually wait at a table at a nearby food court while his wife was in the salon.
This time, Davis went to a nearby men's room where he was allegedly approached by Berrioz.
There was a confrontation and Davis was stabbed multiple times, suffering stab wounds to the chest along with injuries to the hairline of his head and face.
Davis stumbled back to the hair salon where he collapsed as the owner started first aid.
"He staggered into our waiting room and he was bleeding profusely from the head and chest. I got towels, wet towels, compresses to try and stop the bleeding," said salon owner Billy Brocco
His assistant called 911 and rescuers arrived within five minutes, Brocco said.