Introduction: Oral health of the mentally retarded (MR) has received scant attention in the literature compared with the normal child even though they are much sufferer. Aim: To assess the impact of various sociodemographic factors on oral hygiene of MR subjects of Bhopal city. Materials and Methods: A descriptive cross-sectional study was conducted among 267 MR subjects enrolled at various institutions of Bhopal city. A pretested proforma was used to record information about demographic data, socioeconomic status, the intelligent quotient of inmates, type of mental retardation, and dietary habits. The clinical examination was done to evaluate oral hygiene of subjects using oral hygiene index-simplified (OHI-S). Descriptive statistics, Student's t-test, analysis of variance and multiple linear regression analysis was applied using Statistical Package for Social Sciences (SPSS) software. Results: The mean OHI-S of MR was found out to be 2.51. Male had mean OHI-S of 2.95 while female had 1.65. Noninstitutionalized had poorer oral hygiene with mean OHI-S of 3.2. According to the degree of mental retardation, profound had the highest OHI-S score, i.e. 3.71 while mild had the lowest score, i.e. 1.01.