The research was conducted at educational tools companies to obtain with the effect of cohesiveness, leadership style and organizational culture on organizational effectiveness, , by using a survey methods with path analysis applied in testing hypothesis. The amount of 417 companies selected by simple random sampling with 120 samples and each sample was represented by its director or owner to fill the data. The research reveals that : 1) there is a direct positive effect of cohesiveness on organizational culture; 2) there is a direct positive effect of cohesiveness on organizational effectiveness; 3) there is a direct positive effect of leadership style on organizational culture; 4) there is a positive direct effect of leadership style on organizational effectivenes; and 5) there is a positive direct effect of organizational culture on organizational effectivenes. Due to this findings it could be drawn that 6) there is a indirect positive effect of cohesiveness on organizational effectivenes through organizational culture; and 7) there is an indirect positive effect of leadership style on organizational effectivenes through organizational culture. The result explain that the cohesiveness, leadership style, organizational culture are the variances of organizational effectiveness. Therefore, it implies that the organizational effectivenes can be improved by developing the cohesiveness, leadership style, organizational culture.