It is important to appropriately assess the adaptive behaviors of individuals with hikikomori (IWH) using parent reports. However, currently, there is no gold standard in the assessment of adaptive behaviors of IWH. This study aimed to: (1) develop the Adaptive Behaviors Scale for Hikikomori (ABS-H); (2) examine the factor structure of the ABS-H; and (3) examine the reliability and validity of ABS-H. A factor analysis and item response theory (IRT) analysis were conducted using data from 761 parents. Reliability and validity of ABS-H were assessed using measures of severity of hikikomori, difficulty in social participation, extent of places where IWH were active, days on which IWH went out, duration of hikikomori and happiness about relationship with one’s child. A total of 26 items were selected and item-trait was examined from the IRT results. Factor analysis identified four group factors. Cronbach’s alpha was found to be .97. Criterion-referenced, convergent and discriminant validity of the instrument were satisfactory. This study suggests that the ABS-H is a reliable measure with acceptable criterion-referenced, convergent and discriminant validity. Further research is needed to clarify the extent to which the ABS-H is sensitive in capturing the changes in the features of hikikomori.