This study investigates the association between Jewish religious observance and several indicators of mental health and psychological well-being among Jewish Israeli adults. Data are from adult (18+) Jewish respondents in the Israeli sample (N = 2958) of the first wave of the Global Flourishing Study (GFS), a 22-nation population survey which will eventually consist of five annual waves of panel data. The GFS Israeli data were collected via a randomized, stratified, probability-based sampling design, and contained dozens of indicators of sociodemographic, socioeconomic, political, religious, health-related, and other constructs. Measures of Jewish religious observance, including religious service attendance, prayer, scripture reading, belief in God, and importance of Judaism, are statistically significant predictors of several single-item indicators of mental health (overall mental health, depression, anxiety) and psychological well-being (suffering, happiness, life satisfaction). Greater religious observance is associated with a higher self-rating of overall mental health, less depression and anxiety, less suffering, and greater happiness and life satisfaction. Nearly all results withstood adjusting for effects of several sociodemographic covariates. These results offer confirmation of prior studies using smaller samples or non-population-based designs and with fewer mental health and religious indicators. They suggest that evidence for a salutary association between religious observance and mental health or psychological well-being among Israeli Jewish adults is consistent with findings in this literature for adherents to other faith traditions throughout the world.