Aims <p>Adverse childhood experiences (ACEs) have been linked to poorer health and well-being across the lifespan. This study examined the associations of two dimensions of ACEs (threat and deprivation) with 30 chronic conditions (CCs) and their multimorbidity. Further, we assessed whether social support availability (SSA) moderated these associations.</p> Subjects and methods <p>This study used data from the Canadian Longitudinal Study on Aging (CLSA). The sample included 38,191 adults aged 45–89 from the CLSA baseline (2011–2015) cohort. Participants self-reported chronic physical health conditions and ACEs. Logistic regression was used to assess associations between ACE dimensions and CC outcomes, including CC domains based on functional and physiological linkages, adjusting for sociodemographic factors. Effect modification by overall SSA was also assessed.</p> Results <p>Of 38,191 participants, 44% reported ≥ 3 CCs, and approximately 36% had CCs spanning ≥ 3 domains of CCs. Compared to no ACE exposure, threat-only and deprivation-only exposures were associated with higher odds of having ≥ 3 CCs and ≥ 3 domains of CCs. Compared to either threat or deprivation alone, exposure to both threat and deprivation was associated with higher odds of ≥ 3 CCs (OR 1.93, 95% CI 1.72–2.10) and ≥ 3 domains of CCs (OR 1.88, 95% CI 1.72–2.05). Exposure to both threat and deprivation was more strongly associated with most CCs compared to exposure to either threat or deprivation alone. At higher levels of social support, the association between ACE dimensions and&#xa0;CCs were weaker.</p> Conclusions <p>Adults exposed to both ACE&#xa0;dimensions and reporting higher social support had lower odds of multimorbidity than those reporting lower levels of&#xa0;social support.</p>