The man has been seen exposing himself a dozen times since June 2013 in the Meadowcroft, Fairford Leys and Southcourt parks.
He was most recently seen on Monday (September 2).
He has also been seen on August 20, 26 and 28.
The man is described as black and in his 20s or 30s.
Anyone who sees the man is advised not to approach him and to call police on 101 or, if a crime is in progress, 999.
If you have any information about any of the incidents call police on 101.