Toohey was initially charged with the infant's murder but was later convicted of her manslaughter and jailed for seven-and-a-half years, with a non-parole period of four-and-a-half years.

He was eligible for release on October 8 last year.

But in a separate judge-alone trial earlier this year before Judge J Bennett, Toohey was also convicted of the sexual assault of the same infant and was jailed for four years and six months (three years non-parole).

That sentence was backdated to March 9, 2016, making Toohey eligible for parole the day after he was sentenced.

The sentence angered the infant's family and prompted an appeal by the DPP.

The appeal was lodged on the grounds that the sentence was manifestly inadequate with the DPP arguing the sentencing judge erred in his assessment of the objective seriousness of the offence and in his application of the principle of totality.

REAL ALSO: Mandurama baby killer Brendan Toohey's parole bid rejected by board

The matter went before the Court of Criminal Appeal in Sydney in July before justices Gleeson, Button and Lonergan, who set aside Judge Bennett's sentence on Friday.

They sentenced Toohey to six years and nine months in jail on the assault charge, with a non-parole period of four years and six months.

Toohey will be eligible for parole on September 9, 2020.

The baby's family attended the appeal hearing in Sydney in July and, for some, sitting through the harrowing details of the baby's death was just too much and they had to leave the court.

They said on Friday while it had been hard reliving what had happened to their beautiful baby, the outcome was worth it.

"Anything is better then the original sentence [handed down in March]," the baby's grandmother said.

"It's still not enough for what happened to her, nothing ever will be.

"But any little bit extra he [Toohey] gets is better than nothing."

The grandmother said she would always be grateful to the detectives and police who worked on her granddaughter's case.

"They were brilliant, every single one [of the police] we dealt with.

"I can't fault them."

She was also thankful to those who worked to get the matter before the Criminal Court of Appeal.

"They've all done a magnificent job, we will always be thankful," she said.