Children with mild developmental disorders sometimes show giftedness. In this study, an original checklist was developed to identify gifted characteristics specific to science learning among twice-exceptional primary school children in Japan. The checklist consisted of 60 items on Attitudes, Thinking, Skills, and Knowledge/Understanding. A total of 86 children from eight primary schools in an urban area in Japan, 50% of whom had Learning Disabilities (LD), Attention Deficit/Hyperactivity Disorder (ADHD), and/or High-functioning Autism (HA), were observed using the checklist. Factor analysis revealed three factors. A cluster analysis with the subscale points of each factor identified three "gifted styles" in science. These were: (1) Spontaneous Style; (2) Expert Style; and (3) Solid Style. LD/ADHD/HA children characteristically displayed a Spontaneous Style while the non-LD/ADHD/HA children were characterized by the Solid Style. In both subject groups, the number of Expert Style children was the lowest with no significant difference in their numbers. Based on the results of this research, this paper discusses the implications of the findings for teaching science to twice-exceptional children and argues the benefits of inclusive science education for children with and without mild developmental disorders. (Contains 2 tables and 1 figure.)