The COVID-19 public health emergency (PHE) caused significant disruptions in the delivery of care, with in-person visits decreasing and telehealth use increasing. We investigated the impact of these changes on mental health services for Medicaid-enrolled adults and youth in Washington State. Among enrollees with existing mental health conditions, the first year of the PHE was associated with a surge in specialty outpatient mental health visits (13% higher for adults and 7% higher for youth), returning to pre-PHE levels in the second year. Conversely, youth with new mental health needs experienced a decline in specialty outpatient visit rates by ∼15% and 37% in the first and second years of the PHE, respectively. These findings indicate that while mental health service use was maintained or improved for established patients, these patterns did not extend to Medicaid-enrolled youth with new mental health needs, potentially due to barriers such as difficulty in finding providers and establishing new patient-provider relationships remotely. To bridge this gap, there is a need for a multi-faceted approach that includes improving service accessibility, enhancing provider availability, and optimizing initial care encounters, whether in-person or virtual, to better support new patients.