Background: Patient satisfaction with diabetes technology is increasingly recognized as a key factor in therapeutic success. Patient-reported outcomes (PROs) are gaining importance in diabetes care and in the evaluation of advanced insulin delivery systems. Objectives: This study aimed to design and validate a new questionnaire, the Insulin Pump Infusion Sets Satisfaction Scale (IPISS), to assess satisfaction with insulin infusion sets among individuals with type 1 diabetes. Methods: The questionnaire was developed by our Diabetology Unit in two versions: one for patient self-reporting and one for caregivers when the patient is too young to complete it autonomously. Content validity was assessed by six healthcare professionals (three diabetologists and three nurses) based on Polit and Beck’s methodology. The Item Content Validity Index (I-CVI) was calculated for both relevance and comprehensibility and was considered satisfactory if expert agreement reached ≥83%. The Scale Content Validity Index (S-CVI) was computed as the average of I-CVIs, with a cut-off value > 90% deemed acceptable. Results: Almost all items achieved 100% positive agreement for both relevance and comprehensibility, except one item in the caregiver version, for which one rater did not provide a rating for comprehensibility (I-CVI = 83.3%). The S-CVI was 100% for relevance in both versions, 99.24% for comprehensibility in the caregiver version, and 100% in the patient version. Conclusions: The IPISS is a content-validated, self-reported tool, suitable for evaluating satisfaction with infusion sets in individuals using insulin pumps, with versions adapted for both patients and caregivers.