Samołęskie Lake is situated in the Poznań Lakeland in Greater Poland Voivodeship, Szamotuły County, Wronki District. The lake adjoins a little village of Samołęż of about 500 residents. The glacial waterbody of over 30ha acreage is a typical tunnel-valley lake having a maximum depth of over 22 meters. It predominantly serves fishing and recreation purposes offering a beach and a sailing center. Near the coastline (not in the direct vicinity) there is a farmland. The objective of the dissertation was to assess the quality of Samołęskie Lake waters that was delivered based on the studies carried out in spring and summer, when the waterbody demonstrates excessive fertility. The studies covered the analysis of the basic physical and chemical parameters of the lake water. The measurement was carried out on a fortnight basis by means of a measurement apparatus such as the photometer and the Secchi disc. The collected results are presented with the use of figures later in this paper, whereas their in-depth analysis allowed to compile and formulate conclusions. The results of studies and analyses lay the foundations to state that the quality of Samołęskie Lake waters requires continuous monitoring and application of remedial and rehabilitation measures.