The deleterious impact of adverse childhood experiences (ACE) may be confounded with frequently co-occurring social disadvantage. In this analysis we test the effects of ACE on adult mental health within a social disadvantage framework, using a population-based survey (n = 7,444; mean age = 55.2 years) from Washington State. We also examined the protective effects of socioemotional support, and the distinct and combined contribution of the measured ACE factors. Results demonstrated sustained impact of ACE on mental health many decades later, even net of social disadvantage and demographic contributors. Protective factors provided both direct and moderating influences, potentially masking the elevated effects of ACE for those with few resources. Toxicity examination of ACE items evinced differential effects of ACE experiences on mental health. These results demonstrate that interventions ameliorating the effects of ACE and bolstering protective resources such as socioemotional support may be effective toward augmenting mental health even late in life.