Concentration of ownership of agricultural land in fewer hands has often been highlighted as a side effect of the increasing capital resources that are allocated to the agricultural sector. One key concern is that, as more land concentrates in fewer hands, the few large actors can exert power on land markets by dominating prices through regulating supply and demand of land. Unfortunately, empirical evidence on the degree of market power on land markets remains scarce, mainly due to a lack of ownership data. We shed light on the concentration of ownership in agricultural land by analyzing the complete cadastral records of agricultural land at one point in time and for one district in the federal state of Brandenburg. We present the workflow to process the cadastral data for subsequent analysis in GIS and statistical software packages. For our study area, we derive relative and absolute concentration measures for the ownership in agricultural land. Our results suggest high relative concentration on the district level with a Gini coefficient of 0.85. Within the district, we see varying degrees of land concentration, albeit spatial clusters of high and low concentration. Our methodological approach holds great promise because it can be expanded to larger areas and different time periods. However, the cadastral data does not allow to infer on the underlying corporate structures, such as those of large investors who may own several agricultural companies. Such corporative structures may, through their local subsidiaries that could be spatially clustered, exert market power to the detriment of local land supply markets. Additional data and analysis using, for example, registers of company registers, need to be combined with the cadastral data to reveal such structures.