This master’s thesis examines the condition and development of supplementary activities on farms within the area of Local Action Group (LAG) Srce Slovenije. In addition, using a questionnaire and semi-structured interviews helps us determine the potentials for further development of these activities. Farm diversification and supplementary activities are marked as significant factors in the preservation of farming and the rural areas and are therefore included in the development programmes. The development of the database related to supplementary activities (farm holders, locations, the extent of business, etc.) is hindered due to defects in the records. The study includes 24 farms that are based on the processing of primary agricultural goods and/or tourism. There is a total of 168 farms in the research area that include 746 registered supplementary activities. Using qualitative and quantitative analysis, we distributed farms into different types (good, average, weak developmental potential) and prepared guidelines for further development of supplementary activities. The issues with managing supplementary activities are often individualised (adapted to the conditions of individual farms) as a result of significant differences in their size, cause and influence on farm development. Positive development rate is characteristic of farms whose managing has recently been trusted to younger generations or complete new entrants into farming. The interconnectedness of farms within the LAG territory is weak, as LAG is perceived only as a vehicle of promotion and not as an option of connection. The content upgrade of two still developing projects is seen as one of the options for increased integration and connection of the supplementary activities on farms within the LAG territory.