The Crillon Peninsula is located in the southwest part of Sakhalin Island and is a poorly explored territory. Despite the small size of the peninsula, environmental conditions in different parts of Crillon may vary. The research materials include 58 relevés from the northwest and southeast subregions of the peninsula. Taxonomic analysis was performed; and ecological patterns of meadow vegetation using the indicator scales of DN Tsyganov and IA Tsatsenkin were identified. Indices of species diversity, dominance, evenness, and the Jaccard index of similarity were calculated. The classification was based on a resemblance matrix of relevés calculated with the quantitative Bray–Curtis index. A total of 121 plant species representing 93 genera and 27 families have been found in the meadow ecosystems on the Crillon Peninsula. Five groups of meadow phytocoenoses were distinguished after classification, and nearly all of them are distributed equally in both research locations. The Crillon Peninsula’s north-west subregion has higher species diversity and equitability indices, whereas the southeast subregion has higher dominance indices. According to the results of the indicator analysis, both subregions of the Crillon Peninsula have the identical climatic and edaphic conditions. Statistically significant differences were obtained only for the regimes of climate continentality, harshness of winter, soil nitrogen richness (at p < 0.01) according to DN Tsyganov’s scales, and for indicators of soil richness/salinity and pasture digression (at p < 0.05) according to the scales of IA Tsatsenkin. These differences are explained by the climatic characteristics of the peninsular coasts and human activities. The results obtained allow us to conclude that data from one study location can be carefully extrapolated to the entire Crillon Peninsula. During the extrapolation process the anthropogenic stress and agricultural development should be considered
