PC Nicholas Pool, 29, admitted three charges of attempting to incite a 12-year-old girl to engage in sexual activity.
The offences happened on three separate occasions while he was off-duty from his role with Cumbria Police, Carlisle Crown Court heard.
Pool, of Newton Rigg, Penrith, was remanded in custody until 18 March. He has been suspended from the force.
A previous hearing was told an undercover officer had posed as the young girl.
The offences happened on 22 November and 11 and 12 December.
A police officer has pleaded guilty to child sex offences.