Shmuli was born in Tel Aviv, Israel, on 8 February 1980. He holds B.Ed. (summa cum laude) in special education and in social-community education.
Shmuli, who completed his mandatory military service in the Israel Defense Forces, is still a reservist in the Armored Corps. He had to miss his first planned speech in the Knesset after being called up for reserve duty in his tank unit.
He took the third spot in Labor Party list in primary elections, held on 13 January 2015, which put him to the fifth spot in party's list for elections On 31 July 2015, after Jeruslaem LGBT Pride Parade stabbing, Shmuli came out as gay. He was the only open gay MK until Amir Ohana from Likud was sworn in as the replacement for minister and MK Silvan Shalom, who resigned after a sexual harassment scandal.