OBJECTIVES To histologically determine the alteration in horizontal mucosal thickness at sites that received guided bone regeneration (GBR) with additional use of collagen matrix and to assess whether bone formation is affected by adding collagen matrix at GBR sites at 8 weeks of healing. MATERIALS AND METHODS Eight weeks after bilateral extraction of maxillary premolars, standardized defects were created on buccal side of edentulous ridges in four beagle dogs. One side was randomly allocated as control (biphasic calcium phosphate plus collagen membrane; GBR only), while contralateral side was allocated as test (biphasic calcium phosphate plus collagen membrane plus an additional layer of collagen matrix). Histologic observations, histomorphometric and micro-computed tomography analyses were performed after 8 weeks. RESULTS Membrane complex comprising residual collagen membrane and adjacent dense connective tissue was observed at both control and test sites. The thickness in the histologic analysis were 1.69 ± 0.23 mm (control) and 1.76 ± 0.07 mm (test) in histologic analysis and were 2.03 ± 0.26 mm (control) and 2.14 ± 0.24 mm (test) in radiographic analysis. The thickness of the membrane complex in soft-tissue layer were 723.0 ± 241.6 μm (control) and 984.6 ± 334.4 μm (test). The percentage of new bone formation were 22.30 ± 5.92% (control) and 25.50 ± 8.08% (test). All measured outcome did not show significant differences between control and test groups. CONCLUSION The addition of collagen matrix on top of standard GBR procedure did not increase the soft tissue thickness and dense connective tissue formation at 8 weeks of healing. Bone regeneration was not affected by the addition of collagen matrix. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000-000, 2018.