Jorrell Simpson-Rowe was one of four people found guilty in Jane Creba's death.
The 15-year-old Creba was shopping with family on Toronto's busy Yonge Street when she was caught in the crossfire of a shootout between rival gangs in December 2005.
Simpson-Rowe, who began serving a life sentence in 2009, had applied for both day and full parole, but had both his requests denied.
The Parole Board of Canada said it was concerned about the seriousness of Simpson-Rowe's offences, his lengthy violent past, his disregard for community supervision conditions and the amount of time he had been in jail with no period of any kind of conditional release.
It said that while the 27-year-old's behaviour was improving, he continued to have difficulty recognizing problematic situations and when it was appropriate to engage or disengage.
The shooting which killed Creba shocked residents and sparked a debate about gun violence in Toronto.
Simpson-Rowe and Jeremiah Valentine were convicted of second-degree murder in the shootout. Louis Raphael Woodcock and Tyshaun Barnett were found guilty of manslaughter.
On the day Creba was shot, Simpson-Rowe and a friend got into an argument with a group of people on Yonge Street, with Simpson-Rowe pulling a gun out from under his jacket and firing the weapon at the group, the Parole Board decision said.
The board noted Simpson-Rowe's past involved a "dysfunctional childhood" and physical abuse.
"You have a history of associating with individuals who are involved in criminal activity and have traditionally looked up to older, criminally entrenched peers for support and a sense of family," the board's decision said. "You have demonstrated your inability to manage your emotions effectively and have resorted to using violence to get what you want."
In reviewing Simpson-Rowe's time in prison, the board said he had been involved in fights with other inmates and had threatened to throw urine at an officer, among other incidents, but had not been involved in a violent incident in more than two and a half years.
In arguing for day and full parole, Simpson-Rowe had said he was determined to never hurt anyone again and leave his former life behind, the board acknowledged.
But Simpson-Rowe's case management team did not support him in his parole applications, noting that while he was managing his behaviour in a medium-security facility, it was not an indication he was ready for release into the community, the decision said.