Although previous evidence suggests that happiness is lower among individuals with obesity, research on the correlates of subjective well-being (SWB) is warranted to increase our knowledge. We aim to explore excess weight (i.e., measured and self-reported body mass index (BMI)), body image and satisfaction, self-stigma, positivity, and happiness among Spanish adults with overweight or obesity. We further aim to investigate the predictors of SWB in this sample. A convenience sample of 100 individuals with excess weight completed self-reports on the study variables and were weighed and their height measured. On average, the participants reported body perceptions revealing minor excessive weight, moderate body satisfaction, low-to-moderate weight-related stigma, and elevated positivity and happiness. BMI and gender/sex independently affected these variables, but there were no significant interaction effects. Furthermore, individuals with overweight or obesity with higher body satisfaction and elevated positivity were more likely to report being happy, independent of their age, gender/sex, weight, and weight-related stigma. Mediation effects were found for body satisfaction and positivity in the relationship between weight and happiness. Moreover, positive orientation suppressed the pervasive influence of stigma on SWB. Our findings confirm the key role of body image dimensions and weight-related stigma for happiness and add support to the relevance of positivity for overall well-being of individuals with excess weight. These results may inform obesity management actions focused on inclusive aesthetic models, combating social stigmatization and enhancing positivity for a flourishing and fulfilling life.