The study examined home and school environmental factors as determinant of social skills deficit among learners with intellectual disability in Lagos State, Nigeria. The study adopted survey research method using a sample size of fifty (50) pupils with intellectual disability who were purposively selected from five special primary schools in Lagos State, Nigeria. The instrument used for the study was a questionnaire (r = 0.902). The findings revealed that all independent variables jointly contributed to social skill deficits among learners with intellectual disability sampled (F(12,48) = 3.141, p< 0.05) which was significant. Followed by parent education qualification with coefficient (ß = -0.388, p < 0.05) which was also significant. Teacher attitude, school library, family size, parent's employment industry, parenting styles, sport facilities, marital status, parent's income and classroom interaction did not have relative effect on the social skills deficit of learners with intellectual disability/ Based on the findings in the study, some recommendations were made which includes that school, parents and society should encourage good social skills that will compensate for social skills deficit among learners with intellectual disability and also reward good behavior.