Miller, who rose to fame in series Prison Break and appeared as Mariah Carey’s love interest in her ‘We Belong Together’ video, broke the news on Wednesday.
In a public stand against Russia’s recent anti-gay laws, the 41-year-old declined an invite to a Russian film festival.
'As a gay man, I must decline,' he wrote in his reply, which was made public by the campaigning group GLAAD.
‘I am deeply troubled by the current attitude toward and treatment of gay men and women by the Russian government.
'The situation is in no way acceptable, and I cannot in good conscience participate in a celebratory occasion hosted by a country where people like myself are being systematically denied their basic right to live and love openly.' he said.
The British-born American actor- who is of African-American, Jamaican, English, German, Jewish, Cherokee, Russian, French, Dutch, Syrian, and Lebanese ancestry (phew!)- referenced his Russian heritage and revealed he has enjoyed visits to the country previously.
However he added that he won’t be changing his stance until circumstances improve.
A spokesperson for GLAAD praised this move, saying:
'Wentworth's bold show of support sends a powerful message to LGBT Russians, who are facing extreme violence and persecution: you are not alone.'
'More celebrities and corporations should follow his courageous lead'
'As people from across the globe continue to speak out against Russia's horrific law, more celebrities and corporations should follow his courageous lead in openly condemning Russia's anti-LGBT law,' he added.
Russian president Vladimir Putin last month signed a bill banning the adoption of Russian-born children by gay couples, as well as classing ‘homosexual propaganda’ as pornography.
Last year he also barred public gay pride events in Moscow for the next 100 years.