The attack took place along a boardwalk near a beach popular with tourists.
US Vice-President Joe Biden was in a meeting a few kilometres away.
The Magen David Adom ambulance service said four of the injured had severe injuries.
"A terrorist, an illegal resident who came from somewhere in the Palestinian territories, came here to Jaffa and embarked on a run along the boardwalk," Tel Aviv Mayor Ron Huldai told Army Radio.
"On his way he indiscriminately stabbed people."