Objective: Despite significant need, those with severe mental illness (SMI) often remain underserved and understudied. Schizophrenia and borderline personality disorder (BPD) stand out as recurring SMI conditions that historically have been difficult to treat. Empirical evidence for therapeutic treatment for each disorder continues to grow and evolve. Group intervention should be incorporated into care due to the format’s empirical effectiveness and resourcefulness. Method: The current article aims to provide clinically relevant information on group modalities with the most substantial empirical support for first schizophrenia (Burlingame et al., 2020) and then BPD (McLaughlin et al., 2019), using recent meta-analytic findings. This is accomplished by first providing a brief history of group treatment for each disorder. Next, current American Psychiatric Association guidelines and current empirical evidence for group treatment of first schizophrenia and then BPD are reviewed. Results: Based on findings, special focus is given to social skills and cognitive remediation for the treatment of schizophrenia and dialectical behavioral therapy for the treatment of BPD. Empirical evidence, treatment content, vignettes, and resources for each of these modalities are provided. Other promising group treatment options are reviewed for the reader to consider. Given the vast diversity within the SMI population and the multicultural significance recognized today, diversity, equity, and inclusion considerations are provided on the highlighted group treatment options. Conclusions: It is the hope of the authors that the reader will have sufficient information and resources to begin an evidence-based group treatment. By doing so, practice and care for the SMI population will expand and improve.