Background: The substance use treatment field needs to keep up with evidence-based practice (EBP) implementation. Guided by the EPIS Framework, an implementation science framework looking at factors that influence the implementation of EBP, this dissertation sought to illuminate the implementation factors that may be barriers or facilitators when implementing EBP. Methods: Chapter 2 consists of a cross-sectional anonymous web survey with substance use treatment providers in California (N=101) and used bivariate regression models and a hierarchical regression model to examine how different attitude domains were associated with substance use disorder treatment (SUDT) providers’ frequency of use of EBP. Chapter 3, using a qualitative approach and situational analysis, explored the implementation factors that relate to implementing MOUD into practice by interviewing SUDT providers in San Diego County (N=21). Chapter 4 utilized the 2019 National Survey of Substance Abuse Treatment Services (N-SSATS), concentrated on only California substance use facilities, and utilized chi-square analyses and multiple logistic regressions to assess the implementation factors related to offering MOUD. Results: In Chapter 2, at the bivariate level, the attitude domains of openness, organizational support, requirements, feedback, and appeal were all associated with more use of EBPs, while negative perceptions of monitoring were associated with less use of EBP. Overall, the attitude domain of the appeal was statistically associated with more use of EBP in the hierarchical linear regression. Chapter 3 found that the themes affecting implementing MOUD included funding, training, service and inter-organizational environments, and organization characteristics. Chapter 4 findings elucidated that less than half (47.4%) of treatment facilities in California offer MOUD. Results demonstrated that private for-profit and accredited facilities were more likely to accept private insurance and less likely to accept Medicaid and other government insurance. Government-owned facilities and facilities that received government funding had lower odds of offering MOUD. Facilities that were accredited, accepted private health insurance, and accepted IHS/Tribal/Urban funds were more likely to offer MOUD. Conclusion: These findings illustrate the need to use implementation science techniques when implementing EBP in the SUDT field. EBP for substance use are continually underutilized. This dissertation's results show that increasing the appeal of EBP, providing more education and training, and having accreditation and accepting private insurance can help bolster the implementation of EBPs. Future directions could look at how to increase attitudes toward EBP in providers and decrease the barriers of funding for MOUD.