This study examined the relationship between motivation and organisational citizenship behaviour using the mediating effect of job satisfaction among selected teachers of public primary schools in Ojo LGA of Lagos State. The quantitative approach was used in which data for this study were collected from 94 teachers from five (5) selected public primary schools in Ojo Local government using Yaro Yemane (1967) sample size determination formula. Three hypothesized statements were tested using the hierarchical regression analysis for data analysis. Results showed that the degree of relationship between the tested variables were strong and positive. Intrinsic factors influence altruism behaviour among employees and extrinsic factors on the hand also affect conscientiousness among the tested teachers. On the mediating effect of job satisfaction, the result showed the Correlations between motivation and OCB were positive as well and very significant (r = -0.609, p > 0.01). the mediating result of job satisfaction reveled that employee level of OCB will increase when they are satisfied with the motivational factors .It is therefore recommends that among others that management of public primary school should introduce an atmosphere where teachers feel satisfied on their jobs. Authorities should increase the other dimensions of job satisfaction through motivation to induce higher level of organisational citizenship behaviour.