Kyle Leonard, 19, a prisoner at Perth, had sentence deferred at Dundee Sheriff Court.
Leonard admitted having sex with three separate children at three properties in Dundee.
The first offence took place on various occasions between two dates in 2013.
The second was between 2013 and 2014, and the third was between two months in 2014.
Sentence on Leonard was deferred until June 7 for reports.