Sofia Sam, 33, and her lover Arun Kamalasanan, 35, both denied killing 33-year-old Sam Abraham, but a $3 diary revealed their possible motive.
When Sam Abraham was found dead in October 2015, it was initially thought to have been caused by a heart attack.
But an autopsy revealed the sinister truth - he had died from cyanide poisoning and had traces of sedatives in his system.
Police alleged he had been drugged with sleeping pills that were slipped into his avocado shake before orange juice laced with cyanide was poured down his throat in his family home.
During a three-week trial, the court heard that Sam had moved with her six-year-old son to Australia in 2012, before Abraham joined them months later after working in Dubai.
Prosecutors said that soon after, Sam started having an affair with Kamalassanan who had left his own wife and children in India and moved to Melbourne in 2013.
Sam claimed she woke to find her husband of seven years dead in the bed she had shared with him.
But in a secret recording heard in court, Kamalassanan made a confession to an undercover police officer who had befriended him, claiming he put sleeping pills in an avocado shake and poison in orange juice.
The court also heard how a $3 diary became an outlet for the couple to secretly profess their love.
'Can you hold me tight? I want to drift away in your love,' Sam wrote in one of the entries.
'I won’t be enjoying my life until I get a life to love with you,' Kamalasanan wrote back.
While the pair both denied that their relationship was anything more than friendship, investigations revealed they had even opened a joint bank account more than a year before Abraham was murdered.
On Wednesday, a jury at the Supreme Court in Melbourne found Kamalasanan and Sam guilty of murdering Abraham.
Upon hearing the verdict, Sam wept while Kamalasanan showed no emotion.
They are each faxing the maximum penalty of life imprisonment, and will be sentenced at a later date.