The Quebec Court of Appeal upheld the guilty verdict against Brandon Pardi in a decision issued on Thursday.
In the same ruling, the province's highest court rejected an attempt by the Crown to appeal the sentence handed down in the case — two years less a day to be served in the community.
"The facts of this very sad case occurred in 2007. The procedure has run its course. It is impossible to see today that there was any error or irregularity justifying the need to change the sentence on appeal," Appeal court Judge Yves-Marie Morissette, one of the three judges who heard the appeal, wrote in a 30-page decision.
"The application for leave to appeal the sentence should be rejected, as should the appeal regarding the verdict."
Pardi's case gained national notoriety when he fought to be tried as a juvenile because the crime occurred on his first day as an adult.
The case wound its way through the courts before the Supreme Court of Canada refused to hear his case and Pardi was tried as an adult.
The victim, three-year-old Bianca Leduc, was struck and killed as she hung Halloween decorations on a babysitter's lawn in a residential neighbourhood just west of Montreal on Oct. 31, 2007.
Pardi's lawyer was appealing the conviction on dangerous driving causing death, handed down in December 2011, claiming the judge had erred by ignoring certain factors in his judgment.
The Crown, for its part, felt the sentence handed down by the judge was inappropriate in June 2012. It had argued for a four-year jail term.
Instead, Quebec court Judge Michel Mercier handed down a sentence of two years less a day with a host of conditions attached including house arrest for the first year. Pardi was also forbidden from driving for three years.
"The sentence rendered, on first glance, is lenient, there is no doubt," Morissette writes. "But it is also true that it falls within the types of sentences for an infraction of this kind."
Pardi and a friend were driving separate vehicles in a residential neighbourhood in Ile-Perrot, west of Montreal, when Pardi lost control while speeding and struck the other car. Pardi's vehicle careened into the yard, killing the girl.
The co-accused, who was a minor at the time, was acquitted after a separate trial heard before a youth court judge.
The defence in the Pardi case argued the death was an accident, while the Crown blamed him for a series of poor decisions. He was driving with a learner's permit and had no experience driving a manual transmission.
Arguments on appeal were heard from both the Crown and the defence last month in Montreal.