This study aimed to determine the relationship between environmental parameters and epiphytic diatoms. Four sampling sites were selected in the littoral region of Lake Egirdir. Macrophytes were taken seasonally from July 2012 to April 2013. Submerged samples (Myriophyllum spicatum L., Potamogeton perfoliatus L., Ceratophylum sp. and Valisneria sp.) were collected for the analysis of epiphytic algae. Twenty-four diatom species were identified in this study. Cocconeis pediculus Ehrenberg was identified as the most abundant epiphytic diatom on the Myriophyllum spicatum L., Potamogeton perfoliatus L., Ceratophylum sp. and Valisneria sp. Besides, physical and chemical parameters of lake water were determined. Water temperature, pH and conductivity varied from 6.9 - 26.3 degrees C, 8.9-9.1, 276.1 - 388.1 mu S/cm, dissolved oxygen values as 11.8 - 9.7 mg l(-1) respectively. Concentration of calcium, magnesium, silicon, nitrate and phosphate ranged 41.3-32.1, 36.5- 41.3, 5.7 -6.1, 1.1- 3.4 and 0.02- 0.43 mg l(-1), respectively. It was concluded that wave motions in aquatic environments and water quality parameters are primarily effective in the distribution of epiphytic diatoms, seasons are important in the development of some species, and macrophytes provide support for the species to attach to the surfaces according to their morphological differences, despite not being very determinative.