The study examined the effect of organizational culture on workers’ effectiveness. One hundred workers participated were 30 are males and 70 females. Their ages ranged between 20 -55 years with a mean age of 26 and SD of 3.24 and cuts across both male and female gender. The instruments used were a self structure questionnaire and the leadership questionnaire designed by Don Clark (2002). Three hypotheses were tested in the study. The results revealed that there was a significant relationship of autocratic managerial leadership behaviour styles and aggressive-defensive organizational culture on workers’ effectiveness (F 1.314 at P< 0.05) and democratic managerial leadership behaviour styles and constructive organizational culture on workers’ effectiveness (F 1.199 at P< 0.05). Similarly there was a significant association of managerial styles and organizational culture on workers’ effectiveness. The result suggests that managerial leadership behaviour styles and organizational cultures have significant impact on workers’ effectiveness (F 0.988 at P< 0.05) and that changes in managerial leadership behaviour styles have an effect on organizational culture up to a certain point were they both remain constant. Hence, the findings concluded that for effective management of modern organization, managers should be able to harmonize their leadership behaviour and the organizational values to achieve the desired effect.