The man, who cannot be identified for legal reasons, denied the two rape charges and took the case to trial in the Victorian County Court.
A jury on Friday returned verdicts after less than two days of deliberations.
Prosecutors said he digitally raped his friend's girlfriend at his Melbourne home in the early hours of January 14, 2024.
The jury was told the woman had consensual sex with her boyfriend at the house but then he organised an Uber and left the property shortly before 2am.
The offender then lied, telling the woman her boyfriend would be returning upstairs because his Uber had been cancelled.
It was the offender who went into the dark bedroom a short time later and pretended to be the woman's boyfriend before digitally raping her twice.
In the days after, the man doctored an Uber receipt to allegedly make it look like the complainant's boyfriend had left the house after 2.30am.
The man admitted forging the receipt but said he did so because he panicked after being falsely accused of rape.
Crown prosecutor Jeremy McWilliams told the jury the man had told a series of lies to try and deflect blame.
He urged the jury to ignore the man's denials and instead believe the alleged victim, who had given clear, consistent and convincing evidence.
Defence barrister David Hallowes SC argued his client was telling the truth and it was possible the woman's mind was playing tricks on her.
The jury retired to begin deliberations at 3pm on Wednesday after hearing seven days of evidence and legal argument.
The 12 jurors returned their guilty verdicts shortly after midday on Friday.
The man slumped in his seat with his head in his hands as the verdicts were delivered, while his mother cried in court.
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