Mourners gathered at First Corinthian Baptist Church in Harlem, with the Reverend Al Sharpton delivering the eulogy.
Sharpton says someone should be "held accountable" for his death during the eulogy.
Myls died January 8 in a Midtown high-rise after his father was jailed and left him in the care of his girlfriend Kryzie King.
She was charged with assault after allegedly telling investigators she had starved him for several days and also bound, beaten and burned him.
An official review of the case revealed that New York City's child welfare agency missed possible signs that the boy was at risk, including the fact his father did a stint in jail after being awarded custody of his son.
The findings stopped short of faulting individual case workers overseeing the care of Myls, but they prompted Mayor Bill de Blasio to announced a list of reforms for the Administration for Children's Services.
"We lost a child in a horrible manner. ... We want to learn from this tragedy and make changes as a result," De Blasio said at a City Hall news conference.
Among the finding was that case workers missed the fact that the father, an ex-con and parolee named Okee Wade, was in jail from September 2012 to February 2013 despite visiting his home nine times during that period. Wade's girlfriend at the time - not the one in charged in the death - told them he was at work, officials said.
De Blasio said he was ordering a review of all cases that include court-ordered ACS supervision. New measures include requiring custodians to appear in family court and get a judge's approval before supervision ends, and expanding ACS's access law enforcement data bases to assess whether caregivers are reliable or not.
Police say Kryzie King tortured the boy before he died.
Wade says he's never heard of King, and that he left his son with a friend named Jane Munroe. Police say Munroe and King are the same person.
Wade had full custody of his son before he was arrested, and he's been given a three-week furlough from jail to attend Myls' funeral.
"The first tragedy is me being locked up, and I couldn't get my son," Wade said. "And I begged them to at least let me get my son, but they said they wasn't going to let me out. Then the other tragedy is my son is murdered."
The boy's body was released to his mother, even though she did not have custody at the time of his death.