Tania Shailer and David Haerewa, who were convicted of manslaughter over the death of three-year-old Moko Rangitoheriri, have had an appeal against their sentences rejected.
The toddler died in August 10, 2015 from injuries suffered during prolonged abuse and torture.
In 2016 Shailer and Haerewa were each jailed for a minimum of nine years and a maximum of 17 years for Moko's killing.
They had initially been charged with murder but ended up pleading guilty to the lesser charge of manslaughter.
In their appeal, both said their sentences were too harsh - Shailer because she suffered mental health issues and Haerewa because he was a secondary party.
However, the Court of Appeal judgment said the sentences were appropriate, and the two should count themselves fortunate that they were not sentenced to life imprisonment, given the "duration, cruelty and physical depravity of this offending by two adults acting together against a defenceless three-year-old child."
Shailer and Haerewa were supposed to be looking after Moko while his mother Nicole Dally-Paki was at Starship Hospital caring for one of her other children.
Haerewa admitted to police that he'd slapped, kicked and stomped on Moko, and confessed he would regularly lock the toddler in a bathroom on his own for hours at a time.
During the trial it was also revealed that Shailer, who was an early childcare teacher, stomped on Moko's stomach and abdomen - injuries believed to have been the main contributors to his death.
The case sparked nationwide marches calling for an end to child abuse, and a petition to scrap the law which allowed Shailer and Haerewa to downgrade the murder charge in exchange for a guilty plea.