This study aimed to compare the clinical outcomes of pharmacist-provided medication therapy management (MTM) services as compared to no MTM services (i.e., standard of care) on outpatient clinical outcomes for patients with diabetes, hypertension, or dyslipidemia. A systematic literature review of PubMed, EMBASE, Cochrane library, International Pharmaceutical Abstracts, PsycINFO, Scopus, CINAHL electronic databases, grey literature, websites, and journals, was conducted from 1 January 2005–20 July 2021. The search field contained a combination of keywords and MeSH terms such as: “medication therapy management”, “pharmacist”, “treatment outcomes”. Studies published in United States, included adults ≥18 years old who received at least one pharmacist-provided MTM consultation and at least one group who received no MTM, and reported pre-specified clinical outcomes for diabetes mellitus, hypertension, or dyslipidemia were included. Of 849 studies identified, eight were included (cohort studies = 6, randomized controlled trials = 2). Clinical outcomes improved with MTM interventions, as evidenced by statistically significant changes in at least one of the three chronic conditions in most studies. Improvements were observed for diabetes outcomes (n = 4 studies), hypertension outcomes (n = 4 studies), and dyslipidemia outcomes (n = 3 studies). Overall, this study indicated that pharmacist delivered MTM services (versus no MTM services) can improve clinical outcomes for patients with diabetes, hypertension, and dyslipidemia.