Cerebral palsy (CP) describes a group of motor syndromes resulting from disorders of early brain development. Physiotherapy is an important part of the management of children with CP. In Bangladesh a single approach therapy has been adopted in any medical institutes as developmental therapy where a developmental therapist assesses the child and provides physiotherapy, occupational therapy, cognitive stimulation, feeding therapy, speech and language therapy to the children according to the need by a holistic approach. There are limited published evidences on effectiveness of developmental therapy among Bangladeshi children with cerebral palsy. So this study was designed to measure the effectiveness of developmental therapy in children with cerebral palsy. A quasi-experimental study was conducted in the department of Pediatrics of Bangabandhu Sheikh Mujib Medical University from February 2009 to May 2010 on 135 children with CP aged 6 months to 3 years. The motor, mental and behavioral functions of the selected children were initially measured by Bayley Scales of Infant Development II. They were reassessed after 3 months and 6 months following developmental therapy. Only 62 (45.9%) children have completed the 2 follow up sessions and hence were evaluated against their baseline motor, mental and behavior score. The study result showed that motor, mental and behavior functions were significantly improved after 6 months following developmental therapy. Nearly half (46.8%) of the children improved on motor skills, 40.3 on mental skills and about 69% on behavior skills. Epilepsy and duration of therapy at home interfered developmental outcome. This study has demonstrated a beneficial effect of single approach developmental therapy for children with cerebral palsy.