Pell, who has maintained his innocence, was sentenced to six years in prison in March after being found guilty in 2018 of sexually abusing two boys over 20 years ago.
The former Vatican treasurer is the most senior Catholic figure ever to be found guilty of sexual offences against children. Until last year, the 77-year-old cardinal was one of closest advisers of Pope Francis, who has promised a "zero tolerance" approach to paedophilia.
The Pope expelled him from his inner circle shortly after the verdict in December.
Defence lawyers on Wednesday presented what they called a "catalogue of impossibilities" as they attempt to overturn the conviction against Pell, Efe news reported.
"The incidents described by the complainant would require such a concatenation of startling, remarkable improbable and even impossible things all to have occurred in the same 10-15 minutes that it is implausible to think that any of these witnesses have simply forgotten such a remarkable day," lawyer Bret Walker said, according to documents released by the Supreme Court of Victoria.
Walker said the accuser's testimony was inconsistent and unreliable, saying there had been "repeated alterations" and that there was a reasonable doubt about the complainant's accusations.
The prosecution, in its statement, denied that the evidence provided was implausible or contradictory.
"The evidence given by the complainant was not only plausible, it was credible, clear and entirely believable as is reflected in the jury's verdict," the Crown said.
Pell was convicted of abusing two boys at the Melbourne's St. Patrick's Cathedral in late 1996 and early 1997.
The cases of abuse against Pell came to light in 2015, when one of the victims filed a report against him with the Victoria Police, claiming that he was sexually abused twice by him, soon after he was named the Archbishop of Melbourne.
The victim, who was a 13-year-old choirboy, said that in December 1996 after Pell officiated a solemn mass as Archbishop of Melbourne, he abused him and his friend, leaving them traumatized for years.
Another victim, who never reported the acts, died of a heroin overdose in 2014.
( With inputs from IANS )