Background: Oncology pharmacists (OPs) increasingly play a role in managing cancer patients, with the availability of targeted oral anticancer agents (TOAs). OPs ensure appropriate indications upon initiation; screen for, anticipate, and mitigate potential drug-drug interactions; manage side effects; and promote adherence. The impact of OPs on adherence to TOAs has not been described. Methods: The Veterans Affairs Corporate Data Warehouse and Cancer Registry were used to: 1. identify Veterans with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL), marginal zone lymphoma (MZL), lymphoplasmacytic lymphoma/Waldenstrom macroglobulinemia (WM), and/or mantle cell lymphoma (MCL) who received single agent TAO for the first time between 2018 and 2021; 2. retrieve patient demographics, disease characteristics, and TAO dispensation information; and 3. identify visits with OPs within a 30-day window of initial dispensation. Dispensation information was used to calculate the proportion of days covered (PDC) during the first 4, 8, and 12 week milestones after initial dispensation. Non-adherence was defined as a PDC < 0.9. A two-sample proportion test and a Wilcoxon rank-sum test were used to compare milestone adherence between patients who visited with an OP at treatment initiation vs those who did not. Results: 1,944 patients were identified, with a median age of 75 years; 98% were male; 1,498 (77%) were white, 244 (13%) were black, and 53 (3%) were Hispanic, rest were other, or unknown. CLL was the most common diagnosis at 1,578 patients (81%), followed by MCL at 162 (8%), WM at 135 (7%), and MZL at 69 (4%). 1,702 patients (88%) received ibrutinib, 110 (6%) venetoclax, 91 (5%) acalabrutinib, and 32 (2%) lenalidomide. Fewer than 5 patients received either idelalisib, zanubrutinib, umbralisib, and/or duvelisib. 1,757 patients had an initial dispensation supply of either < 28 days or 28-30 days and were used to conduct the adherence analysis; of those 702 had met with an OP at therapy initiation. In the 239 patients with a dispensation day supply < 28 days, patients who met with an OP had higher 4, 8, and 12 week adherence rates (97%, 96% and 92%) compared to those who did not (82%, 75%, 72%); odds ratios (OR) 8.8, 7.7 and 4.7 respectively (all with p < 0.01). In the 1,518 patients with a dispensation day supply of 28–30 days, patients who met with an OP also had higher 8-, and 12-week adherence rates (96% and 91%, resp) compared to those that did not (87%, 79%); OR 3.4 and 2.6 resp, both with p < 0.01. Conclusions: Visiting with an OP upon TAO therapy initiation was associated with a clinically and statistically significant increase in adherence at 4, 8, and 12 weeks after first dispensation. To our knowledge, this is the first study to quantify the impact of an OP on non-adherence in a real-world setting. Our findings suggest a critical need to integrate OPs TAO therapy initiation workflows.