Former Capital + Merchant director and chief executive Owen Tallentire, who is in his mid-60s, was also found guilty of two charges and sentenced to five years in jail.
Following sentencing the defence brought the case to the Court of Appeal, where it was argued last month before Justices Terence Arnold, Lynton Stevens and Rhys Harrison.
However, this appeal was rejected today.
"The Messrs Nicholls and Douglas have been convicted by theft by a person in a special relationship to the sum of $19.76 million. Mr Tallentire has been convicted of theft of $12.1m. Simply put, this is theft on a grand scale," the Court of Appeal judgment said.
The transactions the directors were involved with "involved an abuse of trust and a clear breach of the criminal law governing theft".
"Offending of this nature has long-lasting impacts on investor confidence, which in turn has damaging effects for the economy as a whole," the judgment said.
During the trio's trial, counsel for the defendants argued the proceedings were very different to other cases where such charges were involved.
Douglas and Nicholls' Queen Counsel Bruce Gray said previous cases with these charges had involved the concealment of transactions and that was not a feature of this trial.
Tallentire's lawyer, Nathan Gedye, went as far as to say that the Crown had "overcharged" by bringing the case in the way it did.
Justice Wylie rejected this, but noted circumstances of the trial were "unique" and that it involved "unusual and untested features".