NBP Director Vicente Vinarao said Teehankee was rushed to the Asian Hospital after being attacked by inmate Benjamin Ocampo at around 1:15 p.m.
Vinarao said the mentally disturbed suspect used an improvised weapon in the attack.
Teehankee, son of a former chief justice, suffered a minor wound in the back.
"The victim was coming out of his dormitory with a visitor, when the suspect suddenly stabbed him," the NBP chief said.
He said the incident happened near the kitchen of the maximum security compound.
Ocampo had been staying at Ward 3, where mentally-impaired prisoners are brought. "He had just recently been transferred to Ward 13."
When asked why he stabbed Teehankee, Ocampo replied he was not fond of "Chinese-looking men."
The NBP chief said Teehankee is now safe and has been taken back to his detention cell at the maximum security compound.
It was in July 13, 1991 when Teehankee figured in a verbal tussle with Roland John Chapman and Maureen Hultman in Dasmariñas Village, Makati.
Teehankee shot Chapman and Hultman, who died at a hospital. – Rhodina Villanueva