Background: To ensure the quality of patient care, the bioavailability of drugs, and the success of the treatment, it is imperative that nurses evaluate the adherence of patients to pharmaceutical treatments using standardmeasurement tools that are integrated into the treatment process. No scale that uses psychometric analyses to evaluate this adherence in patients who are on oral chemotherapy is currently available. Purpose: This study developed and tested the validity and reliability of a Turkish version of the standardized Oral Chemotherapy Adherence Scale (OCAS), a tool that may be used by healthcare personnel to better evaluate patient adherence to their therapies. Methods: We developed and examined the validity and reliability of theOCAS using a sample of 306 patients with cancerwho were receiving oral chemotherapy. A literature reviewwas conducted to generate the items. An expert panel evaluated content validity; preimplementation was used to evaluate face validity, factor analysis was used to evaluate construct validity, and criterion validity was evaluated using theMedication Adherence Self-Efficacy Scale. Results: The Cronbach’s alpha calculated forOCAS (19 items) was .738. A highly significant and positive correlation was observed between the testYretest scores of the participants. A positive significant correlation was observed between the total scores of the participants obtained from OCAS and Medication Adherence Self- Efficacy Scale. As a result of the factor analysis performed for the construct validity of the scale, three factors were defined that accounted for approximately 43% of the total variance. Conclusions/Implications for Practice: TheOCAS has acceptable psychometric properties and is appropriate for use in research and clinical practice settings to evaluate patient adherence to their therapies.