Selective mutism (SM) is an anxiety disorder characterized by the failure to speak in specific situations in which speech is expected despite speaking in other settings. Although typically verbal at home, children with SM often vary their speech across other settings and will often use nonverbal communication. SM tends to remit before adulthood; however, a history of SM in childhood is associated with poor developmental outcomes, including continued psychopathology and social difficulties. Results from prior SM treatment research suggest that the disorder is difficult to treat, and many treatment programs are lengthy, which may significantly burden families. Recent efforts have been made in a university setting to treat children with SM using a short, intensive group formatting with promising results. However, many expert SM clinicians work in private practice and other community settings. Thus, it is important to evaluate the effectiveness of intensive group treatment for SM in outpatient community settings. Importantly, intensive group treatment for SM (e.g., camps) may not be feasible for many families, and operating such programs may not be feasible for many community practices. Weekly group treatment for SM may be a more viable alternative, but its effectiveness is unknown. Understanding the effectiveness of intensive and weekly SM treatment programs, as well as factors related to their implementation in a community setting, may provide clinicians with valuable information to guide their service offerings and treatment recommendations. This study used a Type 1 hybrid effectiveness-implementation design to evaluate the preliminary effectiveness of intensive and weekly treatment programs for SM and to gather qualitative information from key stakeholders about potential barriers and facilitators to implementing these two program formats in an outpatient community private practice setting. Qualitative data from the current study suggest that key stakeholders find the group programs acceptable, appropriate, and feasible for the treatment of SM in community private practice settings. However, quantitative results are mixed. Case-level analyses of the intensive and weekly group programs reveal considerable variability such that only some children demonstrated clinically significant improvement. Results may support the intensive program as a possibly effective adjunct treatment program for children with SM and suggest limited clinical value for the weekly program in its current design.