For lethal means safety counseling interventions (LMSC) to reduce population-level suicide rates, interventions must be deployed across many settings and populations. We conducted a systematic search in six databases to review the current state of LMSC interventions across study designs, settings, messengers, populations, and injury prevention levels (e.g., universal). Eligibility criteria were: any individual or group receiving a LMSC intervention involving a human-to-human component aiming to influence adult behaviors related to lethal suicide methods, and outcome assessment of storage behaviors and/or suicidal self-directed violence (SDV). Risk of bias was assessed using the Effective Public Health Practice Project (EPHPP) quality assessment tool. A descriptive synthesis approach was used for analysis. Twenty-two studies were included that reported medication and/or firearm storage behaviors and/or SDV following LMSC. Fourteen of the 19 studies assessing behavioral change reported a significant improvement in safe storage behaviors, and all studies measuring acceptability reported that participants found the interventions favorable. Quality of evidence was limited. No studies were rated low risk of bias, and 77% were rated high risk of bias. There was substantial heterogeneity in the settings, populations, injury prevention levels, delivery methods, and intervention elements. Many included studies focused on caregivers of pediatric populations, and few studies assessed SDV outcomes. Higher quality trials conducted across a variety of settings, particularly those focusing on adults at risk of suicide, are needed. There was no funding for this review, and it was preregistered on the International Prospective Register of Systematic Reviews (PROSPERO) (ID: CRD42021230668).