Background: As yet, there has been little research on the association between physical multimorbidity (the co-occurrence of two or more physical illnesses) and suicide, and results have been mixed. This study examined if physical multimorbidity is associated with suicidal behavior in the general population in the United States. Method: Data were analyzed from 15,311 adults that were obtained from the Collaborative Psychiatric Epidemiology Surveys (CPES). Information was obtained on nine self-reported physical health conditions and lifetime suicidal behavior (suicidal ideation, plan, and attempts). Logistic regression analysis was used to examine associations. Results: An increasing number of physical health conditions was associated with higher odds for suicidal behavior. Compared to those with no physical conditions, individuals with ≥ 4 physical illnesses had 2.99, 4.82, and 4.39 times higher odds for reporting suicidal ideation, a suicide plan, and suicide attempts, respectively. An interaction analysis showed that for suicide attempts the association was stronger in younger rather than older adults. Limitations: The data were cross-sectional and information on physical conditions and suicidal behavior was self-reported and may have been subject to reporting bias. Conclusions: As multimorbidity has increased in recent decades in the United States, alerting medical practitioners to the increased risk of suicidal behavior in adults who have multiple medical conditions as well as screening for suicidality in this group may be important preventive measures to help reduce suicidal behavior in the general population.