Officers Troy Tomlin and Aaron Straughn were found guilty on three counts each, relating to the assault at the Perth Watch house in 2008.
Speaking immediately after the verdict, taser victim Kevin Spratt says he has waited five years for justice.
"I'd like to thank the media for covering this story I really appreciate what you've done for bringing this story to Australia the world from the bottom of my heart thank you very much," said Mr Spratt.
Katie Wood from Amnesty International Australia says that tasers should not be used on individuals held in police custody.
“We welcome the decision or the finding of the court in relation to the tasering of Mr Spratt, where the court actually found that these police officers in the deployment of the taser had actually acted unlawfully. Amnesty International believes that tasers should not be used on people when they are restrained or otherwise held in custody,” said Ms Wood.
Both Mr Tomlin and Mr Straughn left the court without speaking to the media, despite receiving what could be seen as a favourable result.
The existing maximum penalty for unlawful assault can be up to three years imprisonment or a $36,000 fine.
The magistrate said he took the previous service of Tomlin and Straughn into account, saying their behaviour on the night was a "gross error of judgment considering how many times they encountered individuals like Mr Spratt throughout their careers".
Officers Tomlin and Straughn were on duty the night Mr Spratt was brought into the Perth watch house and refused a strip search. What followed was described by the judge as a dynamic situation that occurred over 90 seconds, when Mr Spratt was threatened with being tasered, then had his knuckles kicked from around the chair he sat on. He was repeatedly tasered up to 12 times.
Using a taser to gain a response from somebody goes against police protocol, and this was the basis for both officers' convictions.
"Tasers should really not be deployed as an alternative to lethal force," Amnesty International's Ms Wood said.
Since the incident, Mr Tomlin and Mr Straughn have both been investigated by the Corruption and Crime Commission, receiving fines and internal disciplining. This conviction will end both their law enforcement careers.