The study of the Caspian Sea's algal flora started in the 1960s. However, over the past 20 years, there has been a significant gap in the study of the algal flora in the Azerbaijani part of the sea. As a result, it is now crucial to expand these studies and compare the obtained data with the previous results. The algal flora of the Caspian Sea has been poorly studied taxonomically. The main goal of our research was to identify the biodiversity of the algae of the Caspian Sea, to examine its taxonomic structure and to determine the influence of some external environmental factors. The article contains new information on the marine macrophytes and microscopic algal flora of the coastal zones of the Absheron Peninsula. During our research, 26 species of algae were identified. Species belong to divisions Rhodophyta (1 species), Charophyta (3 species), Cyanobacteria (3 species), Chlorophyta (10 species) and Bacillariophytina (subphylum) (9 species). Chlorophyta division was the dominant group, constituting 38.5% of algal flora, followed by Bacillariophytina (subphylum) ‒ 34.6%, Cyanobacteria ‒ 11.5%, Charophyta ‒ 11.5%, and Rhodophyta ‒ 3.9%. The leading families of the algal flora were Oscillatoriaceae Engler, Spirogyraceae Bessey, Cladophoraceae Wille and Naviculaceae Kützing.