Most Wanted Roy Lawrence Piechocki arrested in Bulgaria
Roy Lawrence Piechocki, 56, has been wanted by Interpol since 2011 for 10 counts of sexually exploiting a minor in the United States.
Piechocki, from Hillingdon in west London, was arrested after being found in a rented flat in a block in Veliko Tarnovo, police said.
He is now being held in the local police detention centre.
The Ministry of Interior said it was the result of a two-month investigation that was a joint effort between local police, the Bulgarian special cybercrime unit and the FBI.
Piechocki had fake identity papers and had altered his appearance, police said.
Bulgarian police also confiscated three computer devices, which they say contained pornographic images of young children.