A former guard of the Gdlan prison in Tbilisi, Vladimer Bedukadze, has been arrested on his arrival at Tbilisi airport from abroad.
His lawyer, Lali Aptsiauri, told journalists her client is in a detention center and ready to fully cooperate with investigators.
Georgian authorities put Bedukadze on Interpol's wanted list in September after he gave the media videos of inmates being tortured in prison.
Shortly afterward, Bedukadze fled to Belgium and asked for political asylum.
He said he wanted to expose the role of Interior Minister Bacho Akhalaya and others in the torture and sexual humilation of prisoners.
Georgian rights defenders said the videos may have been used to blackmail inmates.
President Mikheil Saakashvili called on Georgians to avoid using the case for what he called "political games."
Based on reporting by Novosti-Gruzia and apsny.ge