Diagnosis of mental illness evokes far greater emotional reaction than other diagnosis. it must be needed to know about its techniques for the staff nurses as well as its importance which provides great contribution of staff nurses to screen out the mental illness in various setting of health care. Objectives: To assess the existing level of knowledge regarding screening of mental illness among staff nurses. To evaluate the effectiveness of video-assisted teaching programme regarding screening of mental illness. To find out the association between pre test knowledge score & selected demographic variables. Materials and methods: The investigator used true experimental research (pre-test post-test one group design). Simple randomized sampling technique used to select the 30 staff nurses in selected hospitals of Vadodara. Self structured questionnaire were used to assess the knowledge regarding screening of mental illness . The conceptual framework for this study was based on modified Imogen king’s Goal Attainment Theory. The data was analysed by using descriptive and inferential statistics. Results: Findings revels that in pre-test staff nurses having on average 19.75% knowledge regarding screening of mental illness 14.47±2.99 and in post-test, average 55.32 % knowledge regarding screening of mental illness and mean score was 22.13±3.44.T calculated value is -8.483 which are more than the tabulated value of 2.75at 0.05 level of significance. So we accept H1 and conclude that there is significant difference between pre-test and post- test knowledge score of staff nurses. It shows the very highly significant and association between pre-test and post-test knowledge score regarding knowledge on screening of mental illness. Hence research hypothesis H1is accepted. Conclusion: Hence the Video assisted teaching programme was very effective tool to promote knowledge and practice regarding screening of mental illness.