Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was reported in Wuhan, China, in December 2019 and continues to spread worldwide. Although several vaccines were developed and are being used worldwide, antivirals are still needed for people who are not vaccinated or who are vaccinated but infected due to insufficient immune responses. Plant-derived natural substances have long been studied to develop drugs for infectious diseases, and accumulated evidences support a possibility that these may well be efficacious in reducing the risk of SARS-CoV-2 infection. In the present study, it was determined whether somatid natural gels (SNGs) prepared from mandarin, ginseng, or garlic inhibit the replication of SARS-CoV-2 in vitro study. Cytopathic effect (CPE) inhibition assay, immunofluorescence assay (IFA), and quantitative real-time polymerase chain reaction (qRT-PCR) were performed to evaluate the effect of SNGs on SARS-CoV-2 replication in cell culture. Among three SNGs, the mandarin SNG had the highest inhibitory effect on SARS-CoV-2-induced CPE, while the garlic SNG showed no activity. When viral protein levels were identified by IFA, mandarin SNG treatment suppressed N protein expression in a dose-dependent manner. In addition, viral RNA copy numbers and infectious viral titers of SARS-CoV-2 were also significantly reduced by mandarin SNG. Our results suggest that mandarin SNG exerts antiviral activities against SARS-CoV-2, implying a possible use of these natural materials as a preventive or therapeutic agent for COVID19.