This paper analyses the level of knowledge management implementation in organizations and the impact of control variables on knowledge management dimensions. In addition, the importance of knowledge management influence on the competitive sustainability of an organization is addressed. The idea of the research is to highlight key factors that affect the effectiveness and efficiency of knowledge management applications in transition conditions. Data for the study were obtained by surveying 520 respondents—managers of all levels from manufacturing enterprises in Serbia. A t-test was conducted in several variations. More precisely, the t-test analysis was conducted on the average assessments of knowledge management dimensions and with specific control variables. The findings indicate that knowledge management dimensions differ in domestic enterprises and foreign enterprises as well as that their impact differs across organizational levels. Financial performance (profitability, sales growth, asset growth, market share, competitive position in a specific industry, productivity, and salaries) was found to be a reliable indicator of knowledge management success. It can be concluded that knowledge management dimensions have an important role in transition countries, and it is evident that effective knowledge management is imperative for the competitive sustainability of an organization.