Occupational health implies not only health protection but also health promotion, emergency care, wide range of preventive, curative services, rehabilitative services, a concept which includes everything that can apply to promote the health and working capacity of the worker. A Quasi–experimental study was conducted to assess the effectiveness of video assisted teaching on knowledge of health hazards. 60 samples were selected using Non–probability purposive technique at L & T construction site in Saidapet and Teynampet in which 30 samples were experimental group and the other 30 for control group. The data was collected by using a self–structured questionnaire by the investigator and were analyzed.Among the 30 samples in the experimental group 20.00% of employees had moderately adequate knowledge and 80.00% of employees had adequate knowledge in post–test, whereas in the control group 73.33% of employees had inadequate knowledge 26.67% had moderately adequate knowledge.‘t’ value shows statistically high significant difference in the level of knowledge at p<0.01 level among the employees. This reveals that video assisted teaching was more effective.