This study examined the Study of Personality and Adjustment Behavior among High School Students in Thiruvallur District.  These study adopted normative survey methods of research participant’s were 300 students randomly selected from various colleges in Thiruvallur District. The Research Instruments used for data collection was Personality questionnaire developed by S. Sathiyagirirajan and Adjustment Behaviour prepared by Peter Robinson tested at 0.05 and 0.01 level of significance. The result showed that there is a significance difference between the Male and Female high school students on their Adjustment Behaviour. The result revealed that there is a positive relationship between Personality and Adjustment Behaviour of high school students.