Purpose <p>The Latinx population in the US is diverse and heterogeneous, yet we know very little about subgroup variations in mental health.</p> Methods <p>We examined the role of established outcome expectancy variables (viz., optimism/pessimism, hope, problem orientation, &amp; future orientation) in accounting for mental health (viz., depressive symptoms &amp; life satisfaction) in three adult Latinx subgroups living in the US, namely, 328 Dominicans, 180 Puerto Ricans, and 157 South Americans.</p> Results <p>Results of regression analyses indicated that outcome expectancy variables, as a set, accounted for large amounts of the variance (31–49%) in depressive symptoms and life satisfaction across all three Latinx subgroups. Based on conducting dominance analyses to identify robust determinants (predictors contributing &gt; 17% of the explained variance) in outcomes, negative problem orientation and optimism were identified as the two most robust determinants of both depressive symptoms and life satisfaction for Dominicans. For Puerto Ricans, optimism was the most robust determinant of both indices of mental health, with hope also found to be an additional robust determinant of life satisfaction in this group. Finally, for South Americans, negative problem orientation was found to be the most robust determinant of depressive symptoms, whereas hope and optimism were found to be robust determinants of life satisfaction in this subgroup.</p> Conclusion <p>These findings make clear that different outcome expectancy variables play varying roles in accounting for mental health across Dominican, Puerto Rican, and South American adults. Accordingly, it would be useful to avoid treating Latinx adults as a singular or uniform group.</p>