Richard Fruin, 36, a convicted paedophile in the United Kingdom, was arrested last October on suspicion of sexually abusing the boys aged eight, 10 and 11-years-old.
He had been teaching English in a private school in the capital for adults and children, despite serving a one year jail term in Britain in 2005 for producing child porn.
Handing down the two-year sentence, Judge Kim Rathnarin said Fruin was guilty of committing "indecent acts" against the boys -- without giving further details of how he lured the brothers to the guesthouse.
"He will be deported from Cambodia after serving the jail term," the judge said, ordering Fruin to pay $2,500 in total fines to his victims.
Fruin denied the charge against him during his trial earlier this month.
Campaign group APLE Cambodia expressed regret that the sentence was not longer but welcomed the guilty verdict and deportation order.
"We can be sure that this man will not hurt any child in Cambodia anymore," said Yi Moden, of APLE.
"The victims do not have to be scared that he will ever hurt them again."
Cambodia launched a drive in 2003 to shed its reputation as a haven for foreign child sex offenders.
Dozens of foreigners have since been jailed for child sex crimes or deported to face trial in their home countries.