Coverage of roots exposed by gingival recession is one of the main objectives of periodontal reconstructive surgery. Connective tissue graft (CTG) is preferred for treating most mucogingival recession defects and could be considered the gold standard. Chitosan is known to be natural polymers and it is available, biodegradable, biocompatible, and non-toxic and has antimicrobial and anti-inflammatory effects. Platelet rich plasma (PRP) is an autologous source of platelet derived growth factor and transforming growth factor beta that play a role in periodontal regeneration. The present study was designed to evaluate and compare chitosan membrane with or without PRP versus CTG in the treatment of Miller Class I buccal gingival recession ≥ 4 mm in width in dogs histologically. Miller Class I buccal gingival recession defects were surgically created in upper and lower canine of dogs. After 4 weeks, the defects were randomly assigned to one of the three treatment modalities, connective tissue graft + coronally advanced flap, chitosan membrane + coronally advanced flap or chitosan membrane + autologous platelet-rich plasma + coronally advanced flap.  . The animals were sacrificed using an overdose of anesthesia for histological examinations according to the following order:  Two dogs were sacrificed at one month post-surgically and two dogs were sacrificed at two month post-surgically. The blocks were processed routinely in a way to obtain a panoramic view of the recession area for histological examination. Histological evaluation of the CTG revealed connective tissue fibers which were parallel to the root surface, and no histological evidence of new cementum, bone or periodontal ligament. On the other hand, histological evaluation of the chitosan membrane or chitosan membrane with PRP revealed new cementum, new bone formation, dense well organized highly cellular periodontal ligament fibers oriented perpendicular to the tooth surface and no migration of junctional epithelium. While CTG is the "gold standard" for root coverage in teeth with gingival recession the histological results of the present study revealed that CTG repaired by connective tissue.  In contrast, the CAF with chitosan membrane with or without PRP was found to have all tissues necessary for regeneration, new cementum, well organized periodontal ligament fibers and new bone formation.