The study aimed to examine the influence of lifestyle on happiness of persons with type-2 Diabetes Mellitus. The research was conducted on 150 type-2 Diabetes Mellitus patents in the age range of 18-85 years. Random sampling method was used in order to select the subject’s for the present study. Survey method was adopted for the collection of data. Lifestyle scale (LSS-BK) and Happiness Scale (HS-RHM) was used to assess the lifestyle and level of happiness respectively. In order to analyse the data mean, SD, “t” test and ANOVA was used. The data analysis showed that there was a low level of adapting lifestyle and an average level of happiness among persons with diabetes mellitus. The present study enumerated the factors that have an influence on lifestyle and happiness among diabetic patients. Henceforth the research findings established a positive correlation between lifestyle and happiness among diabetic patients which will further aid future research endeavours in this area.