Legal responsibility in nursing practice means is the way in which nurses are obligated to obey the law in professional activities. It is always better that all nurses should understand the legal responsibilities. Objective are to assess the knowledge regarding legal aspects of psychiatric nursing among third year B.Sc. Nursing students & To evaluate the effectiveness of self- instructional module on knowledge regarding legal aspects of psychiatric nursing & To associate the pre-test knowledge score with the selected demographic variables. A quasi -experimental research design with 60 samples selected by convenient sampling technique were and Data collection was done by self -structured questionnaire regarding third B.Sc. Nursing student the overall result shows that pre-test 60% of the respondents had Moderate knowledge (33.3%) of the respondents had inadequate knowledge and (6.7%) of respondents had adequate and none knowledge and in post-test (93.3%)of the respondents had Adequate knowledge ,(6.7%) of the respondents had Moderate knowledge and none of respondents inadequate. The mean of pre-test knowledge 13.08 and standard deviation was 4.36. The post mean score 23.07 and standard deviation was 2.48. 56(93.3%). Conclusion the study from the finding that Self- Instructional Modules has found to be effective in significance gain in the knowledge among third year B.Sc. Nursing students reading legal aspect of psychiatric nursing.