Background: Narrow band ultraviolet B (NB-UVB) is a crucial and effective line of treatment 5 for non-segmental vitiligo. 6 Objective : To compare the effect of adding platelet rich plasma (PRP) injections versus 7 microneedling sessions on the response to NB-UVB in patients who stopped giving response or 8 did not give response from the start. 9 Patients and Methods: An intrapatient randomized comparative study including thirty patients 10 with stable, non-segmental vitiligo. Three lesions were assessed in each participant and randomly 11 allocated to undergo PRP injections or microneedling every 2 weeks for 4 sessions. The third 12 lesion was left as a control. Throughout the study, all lesions were subjected to NB-UVB three 13 times a week. Photographic assessment by an independent dermatologist, and a patient 14 satisfaction questionnaire were used to assess repigmentation. 15 Results: PRP injection showed better results than microneedling in terms of repigmentation, 16 complications and patient satisfaction. Mean percent of repigmentation in PRP, microneedling 17 treated and control lesions were (58.17 + 21.52, 24.5+ 18.77, 15.17+ 13.49 respectively, p < 18 0.001). The onset of repigmentation was earlier in the PRP injected lesions compared with 19 microneedling (3.97+ 1.607, 7.8+ 2.683 weeks, respectively, p