Approximately 30% of children with developmental disabilities (DD) or Autism spectrum disorder (ASD) exhibit numerous types of problem behaviors, such as self injury physical aggression, disruptive behavior, and noncompliance (Gadow, Devincent, Pomeroy, & Azizian, 2004; National Research Council, 2001). For those who also meet diagnostic criteria for intellectual disability, the percentage may be even higher. Problem behaviors are considered as a detrimental factor that can severely impede a child and caregiver’s psychophysiological well-being, child’s learning, and social interaction within various environments, such as home settings (Horner Carr, Strain, Todd, & Reed, 2000; Riechle, 1990). The primary factor underlying problem behaviors may be limited communication skills, and such maladaptive behaviors seem to be maintained by inappropriate learning processes that occur within a child’s relationship with his or her caregivers (Bergman, Zager & Gerdtz, 2005; Carr et al., 1999; Horner et al., 2000, 2002; Carr, Strain, Todd & Reed, 2002; Kazdin, 2001; Kazdin & Weisz, 2003; Ozonoff, & Cathcart, 1998; Wolf & Neisworth, 2005). These findings suggest that problem behaviors may be a result of inappropriate learning, and, thus, may be improved through a relearning process, combined with behavioral analytic techniques. The conventional practice for clinicians to treat problem behaviors was taking a tertiary preventative intervention approach, which involves intervening directly after such behaviors have already been severely developed. More recently, however, a primary preventative intervention has started to receive much attention. This approach aims to prevent occurrences of problem behaviors through training programs offered to parents or caregivers. It also attempts to help manage any reoccurrence of them. (Brenton, & Tonge, 2005; Briesmeister & Scahefer, 1998; Feldman, & Werner, 2002; Kasari, Feeman, & Paparella, 2006; Koegel, Bimbela & Schreibman, 1996; Shieds, 2001; Siller & Sigman, 2002). Moreover, for successful dissemination of such programs, training programs delivered in a group format, rather than in an individual format, have obtained popularity. The purpose of the study is to assist children with DD or ASD and their parents by implementing a behavioral parent training, which is based on learning principles. The program aims to prevent occurrences of problem behaviors and manage such problems effectively at an early state. The progress and outcome of the present study not only provide implications of how behavioral parent training can be adapted to manage different aspects of difficulties that children with DD experience (e.g., learning, physical activities, cognition), but it also offers information on the delivery of the format and structure of the program. Further, the study attempts to develop a program that prevents problem behaviors that are characteristic of child with DD or ASD, validate the effectiveness of the program, and develop a manual that can be easily employed by a professional with a bachelor or master’s degree in clinical settings. The study will be a pioneering attempt at implementing a group-based program, in which its treatment efficacy has been empirically verified, based on research that examined child’s behavioral problems observed in clinical settings of Korea. The circumstances of clinical settings in Korea are that popular treatments, in which their effectiveness has not been validated, are often delivered to the public. In view of the present domestic affairs, we accentuate the importance of conducting treatment outcome studies and developing an effective program that can be generalized in different settings.