Placental extract, which contains various bioactive agents, is thought to be a prospective medicine for systematic and oral diseases. However, in-depth information regarding its mechanisms with respect to treating periodontal diseases is not available, thereby hindering its reliable application in dentistry. Here, we demonstrated that P-placental extraction（Nippon Meat Packers Inc）, isolated from porcine tissue, increased collagen type-1 production and hindered pro-inflammatory cytokine secretion from primary human gingival fibroblasts（HGFs）in vitro. HGFs were isolated from a 65-year-old patient who had undergone surgery due to chronic periodontitis. The cells were exposed to media with or without 20-2000 μg/mL P-placental extraction for 24h. No cytotoxic effect of P-placental extraction was observed up to 200 μg/mL；cell viability was attenuated at the dose of 2000 μg/mL. When P-placental extraction was used at the noncytotoxic concentration of 200 μg/mL, it significantly enhanced collagen type-1 production by HGFs within 24h. Secretion of the pro-inflammatory cytokines interleukin（IL）-6 and IL-8 by HGFs treated with lipopolysaccharide（LPS）decreased when P-placental extraction was present in the medium. The results suggest that the mechanism underlying the therapeutic effect of placenta against periodontal disease is partially due to modulation of the cellular function of HGFs.