This split-mouth randomized clinical trial was designed to evaluate dimensional bone alterations following horizontal ridge augmentation using Xenograft with or without autogenous bone, both associated with A-PRF+ and covered by non-resorbable membrane for the rehabilitation of atrophic anterior sites of the jaws with dental implants. The study enrolled 19 patients with 42 horizontal bone atrophy sites requiring guided bone regeneration (GBR) procedures. The first side of each jaw was randomly received a combination of 70:30 xenograft with particulate xenograft, A-PRF+, and covered by a Ti-d-PTFE membrane, while the parallel side received particulate xenograft alone, A-PRF+, and covered by a Ti-d-PTFE membrane. After nine months of healing, the membranes were removed in a second stage surgery and implants were inserted. Radiographic examination (cone-beam computed tomograms) was performed before the surgery (T0), immediately after bone grafting procedure (T1), and at 9 months (T2), to evaluate the amount of horizontal bone width gain and graft reduction. Nineteen patients completed the study. Both groups developed enough bone ridge width. There was no statistically significant difference in bone gain obtained in the xenograft group when compared to the 70:30 mix group group immediately after surgery (P > 0.05) or at 9 months (P > 0.05). Both groups showed minimal bone reduction nine months post-surgery with no difference between the two groups (P > 0.05). Based on the data from this study, both 70:30 xenograft and autogenous bone graft mix and 100% xenograft showed identical clinical results in the treatment of horizontal bone defects, using the GBR technique. The presence of the autograft in the mixture did not provide any additional benefit in terms of bone gain or reduced graft absorption.