AimTo investigate the associations between Grit, connectedness, and parental involvement in Thai adolescents. Grit, perseverance, and passion for long-term goals are predictors of academic success and health. There is a small but developing knowledge of the predictors of Grit in Asia, especially Thailand. This paper investigates the proposition that connectedness and parental involvement are positively associated with Grit.MethodA total of 2,839 lower secondary (grade 8), higher secondary (grade 11), and vocational (year 12) students from 21 schools in Chiang Mai, Thailand participated in a survey that measured Grit using the Short Grit Scale. Bivariate analysis was conducted using the t-test, ANOVA, or Kruskal–Wallis H test as appropriate. Multiple ordinary least squares linear regression analysis was performed to determine factors associated with Grit.ResultsSatisfactory relationships with teachers (p = 0.01), parental support (p = 0.03), interest in school (p = 0.01), having been asked by parents to do homework (β = −0.69; p = 0.012), and having been told by parents that they had done something bad (β = −1.09; p = 0.02) associated with Grit. These findings can aid in design of tailored interventions to improve Grit in Thai adolescents.