Mother-son incest as well as female pedophilic disorder remain underrecognized and misdiagnosed. This is the case of a female child abuser who suffered from hypersexual disorder and mental retardation and whose son was viewed as a substitute transitional sexual partner. Our clinical case shared some common features with female sex offenders previously described in the literature but the association of sexual gratification and hypersexuality without pedophilic fantasies is quite uncommon in female child abusers.