This study was to develop tablet personal computer-based cognitive training programs for children with developmental disabilities whose cognitive age is less than 4 years. Twelve cognitive training programs (named Injini) were designed comprising cognitive domains that included attention, visual and auditory perception, memory, executive function, language, and reasoning. In addition, programs related to learning experiences, such as self-regulation, role play, learning of number, and letter/shape concepts, comparison, classification, and pattern matching, were included. Six of 12 programs comprised approximately 10 levels for each program, with different difficulty levels. Other programs consisted of universal tasks that did not have a difficulty level. To ensure that the difficulty level was appropriate, we pre-tested the pilot version of Injini among 80 children with typical development aged 18 to 41 months. After modifying the pilot version, we developed the final version and tested it among 80 children with cognitive impairment whose cognitive age was 18 to 41 months. All children were assessed using the Bayley Scales of Infant and Toddler Development to determine their development and cognitive age. The difficulty level analyses in children with typical development revealed several inappropriate results wherein the success rate did not decrease with increase in level in some programs. After adjusting the difficulty level, the analyses in children with cognitive impairment demonstrated that the success rate gradually decreased with increasing level in all programs. Cognitive training programs for children with developmental disabilities were successfully developed.