To present the structure and outcomes to date for the Psychiatric Assessment and Brief Intervention (PABI), a pilot program developed at University of California, San Francisco, to improve access of primary care patients to mental health services. PABI offers diagnostic evaluations and brief (up to 3 months) evidence-based treatment, including pharmacologic management and psychotherapy, to medical patients 18 years of age and older. Core PABI features are ensuring prompt access, actively partnering with patients and referring providers, and coordinating seamless transitions of care. Demographic and clinical variables and outcome indicators were collected for all patients seen in PABI from October 2015 to June 2017. Descriptive statistics and mixed-effects linear models were used to analyze the data. During the study period, 139 patients (54% women, mean [SD] age of 48.2 [17.5] years) with a mean of 2 DSM-5 psychiatric diagnoses each (range, 1-5) were seen. Mean time to access was 8 days, with a mean length of stay in the program of 11 weeks. Compared to baseline, final behavioral health measure scores showed significant improvement: the mean Patient Health Questionnaire-9 score decreased by 5.9 points (95% CI, 4.6-7.2), and the mean 7-item Generalized Anxiety Disorder scale score was 4.4 points lower (95% CI, 3.2-5.6; both P values < .0001). This brief psychiatric treatment program provides prompt access to quality mental health care for patients with medical comorbidities. Results to date suggest that this program leads to significantly improved clinical outcomes. Further research is needed to determine its long-term sustainability and generalizability.