Mental retardation (MR) is a condition where the cessation of mental development occurs or is incomplete, mainly marked by the disruption of skill during development, affecting intelligence (cognitive, language, motor, and social abilities). Cerebral palsy (CP) is a group of motoric and physical posture development disorders caused by cerebral development impairment. Children with MR frequently have a co-occuring CP. In this case report, a 6 years old girl consulted to the psychiatric department because of emotional irritability. The patient was seen limping on one side, screaming, moving everywhere, uncooperative, imperfect sentence, not able to draw well and would scream in anger if not get what she wants. Since birth, she has weakness on her left side of the body, has a gross motor delay, still unable to take off her clothes. The patient was born through vaginal delivery at 8 months gestational age with premature rupture of membrane, cried spontaneously. During the pregnancy, the mother had routine antenatal care from the midwife and was said to be fine. The patient was diagnosed with moderate mental retardation with a significant behavioral disorder that requires attention or therapy. Pharmacological therapy of risperidone 0.3 milligram, vitamin B6 10 milligram, and folic acid 1 milligram all are taken once daily oral. MR can have a co-occuring CP and need to be treated. The treatment should consist of mental and physical therapy, as well as rehabilitation.