A judge has found Jonathan Hope and Lisa Guerin not guilty of manslaughter and criminal negligence charges.
The parents of Summer Hope, who died in 2006 after drinking methadone, were convicted on Failure to Provide The Necessities of Life.
For two weeks, court heard evidence detailing how the toddler gained access to the methadone, which belonged to her father, and what was done in the hours after she became sick.
Jonathan Hope admitted to spitting some of his daily dose of methadone, which he was taking to fight a painkiller addiction, into a coffee cup and taking it home with him.
Prosecutors argued that Summer's parents knew she had consumed the potentially deadly drug but didn't get her help.
But in handing down his decision, Justice Earl Wilson said there wasn't enough evidence to prove the pair knew how dangerous the drug could be.
Wilson said both parents should have done more to get the toddler help but ruled that they weren't criminally negligent.
Both Hope and Guerin were relieved when the verdict was read out.
Summer's godfather Terrance Lynn called the ruling "ludicrous".
The conviction on Failure To Provide The Necessities Of Life can carry a prison sentence of up to five years.
Sentencing arguments are scheduled for next week.
