BACKGROUND: The tiger population in Southwest Primorye is small and predominantly isolated from the main Sikhote-Alin population, which constitutes approximately 90% of the wild Amur tiger population. By 1996, this population declined to fewer than 10 individuals, but it has since grown and expanded into nearby habitats, now numbering over 50 individuals. Therefore, the regular genetic monitoring of this population is essential, as it has grown from a few founding members and remained geographically isolated. METHODS AND RESULTS: Genetic diversity was assessed using nine heterologous microsatellite markers amplified from non-invasively collected samples of 20 individual tigers. The Southwest Primorye tiger population exhibited moderate genetic diversity, with allelic richness (Na) at 3.67 and observed heterozygosity (Ho) at 0.63. Additionally, we detected a slight tendency toward heterozygosity excess at several loci, with an overall negative FIS, which may be influenced by recent genetic admixture or subtle population structuring. comparative assessment between our study and Sugimoto et al. (2012) revealed a marginal increase in genetic diversity over time, suggesting improved genetic health of the population, potentially due to genetic exchange with other populations. CONCLUSIONS: The significant growth and expansion of the Southwest Primorye tiger population into adjacent areas of Northeast China over the past two decades suggest a positive population trajectory. This modest increase in genetic diversity indicates a potentially favorable population condition. However, continuous genetic monitoring remains essential to track genetic trends, detect potential risks, and inform conservation strategies. This study highlights the need for ongoing evaluations to ensure the long-term survival of the Amur tiger population in Southwest Primorye.