The relationship between social capital and sustainable development challenges is of special importance. However, social capital is a complex phenomenon that is analyzed in different contexts and cannot be investigated with the use of a single variable. Social capital is difficult to define, which is why the selection of variables for measuring social capital can be problematic. The aim of this study was to analyze variations in social capital at the regional level. The study was conducted in Poland, and it covered all 16 Polish voivodeships (regions) where social capital was evaluated based on five measures: civic engagement in political and social life, degree of selfless behavior, sense of security and social confidence, formation of social structures, and the observance of social norms (external factors), and attitudes (internal factors) that foster desirable social interactions. The correlations between the above measures were also determined. Composite indicators of the analyzed measures were developed with the use of the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method. The results were used to rank Polish voivodeships and group them into three classes based on the corresponding values of the adopted measures. Pearson’s correlation coefficient was used in the correlation analysis. The analysis involved a total of 26 indicators based on the data provided by Statistics Poland, the National Election Committee, Social Diagnosis project, and Moja Polis website. Polish voivodeships not only differ considerably in terms of the evaluated measures of social capital, but are also characterized by significant internal variation within each measure. The majority of Polish voivodeships were grouped in class II denoting average values of the evaluated measures, which could suggest that Poland is deficient in social capital. The Pomeranian voivodeship scored highest and the Łódź voivodeship scored lowest in the analyzed measures of social capital. A significant correlation was observed only between civic engagement in political and social life versus the formation of social structures and the observance of norms and attitudes that foster desirable social interactions.