The purpose of this study was to estimate the effect of our post-acute comprehensive intensive inpatient treatment (Program A) on persons with acquired brain injury in the hospital. Program A, designed for work or school, consists of daily six hours sessions for three months, personal and group sessions, and family support. It was designed to build cognitive and behavioral skills through a transdisciplinary approach and 17 patients with acquired brain injury were enrolled in the program. Seventeen program non-participants were selected as our control. Cognitive functions were measured with FIM, WAIS-III, RBMT, and TMT before and after the program. Significant cognitive improvements (especially attention) and increased societal participation were obtained for the Program A participants compared with non-participants. Considering that Program A improved both the cognitive function and level of social participation in program participants, we suggest that it is valuable to perform intensive treatment programs in an inpatient condition for acquired brain injury patients.