Introduction: Neither validated scales nor scales translated into Spanish currently exist to evaluate the perception of quality care in people receiving outpatient chemotherapy, despite their usefulness in evaluating the care provided by nurses and in promoting changes in the delivery of these services. Objective: To design and validate the novel Care Quality Ambulatory-I (CQAMB-I) instrument in outpatient chemotherapy services. Materials and methods: This is an instrument validation study carried out in three stages: literature review, design, and validation of the instrument. Content validation was performed with 14 specialists with at least a master’s degree and experience in chemotherapy or quality services; face validation was carried out through a pilot test with 31 participants diagnosed with cancer who received curative chemotherapy, and construct validation was carried out through an exploratory factor analysis with 436 users who received outpatient chemotherapy with curative intent. Results: A total of 15 items were removed in the content validation stage; none were removed in face validation. In construct validation, participants had a median age of 56 years, a median treatment time of 5 months, and breast cancer was the most commonly diagnosed form of cancer. Eighteen models were run, 30 items were removed, 6 factors emerged, and a KMO of 0.80 and a Cronbach’s alpha of 0.82 were obtained. Conclusion: The CQAMB-I proved to be valid and reliable for the evaluation of quality care in outpatient chemotherapy services. Additionally, it enabled expanding the conception of such care beyond the attributes of structure, process, and outcome.