Microalgae are photosynthetic microorganisms that can be cultivated in a controlled condition and used as animal feed, biofuel production, nutraceutical, bioactive chemicals, wastewater treatment and other environmental-friendly applications. This study was aimed to isolate and screen local microalgae species suitable for mass cultivation in outdoor open pond systems sampled from the South-Eastern gulf of Lake Tana from January-June (2020). The water samples for isolation of microalgae were collected from shore, center and river mouths of the Lake. The isolation of microalgae was done using agar plating technique, serial dilution and capillary pippet methods in C-medium followed by incubation of 2500 Lux (12 light: 12 dark) fluorescent light and 24 oC temperature. Thirty five isolates were established after repeated dilution, pippeting and streaking on basal and agar C-media. Eight microalgae isolates were selected for growth and productivity evaluation namely Stichococcus species, Synechococcus species, Scenedesmus species, Scenedesmus armatus, Chlorella species, Ankistrodusmus species, Monoraphidium species and Chlamydomonas species because they were successfully cultivated at high density and purity through microscopic inspection and OD readings. These eight strains showed great heterogeneity in specific growth rate (µ) and biomass productivity (p<0.001). Chlorella species (TCO16) and Stichococcus species (TC12) showed higher µ that is 0.182 ± 0.03 and 0.153 ± 0.04 day-1, respectively. Chlamydomonas species (TC12) and Synechococcus species (TCE14) showed the highest biomass production (1013 ± 94 and 934 ± 94 mgL-1), respectively. Chlorella species, Synechococcus species and Ankistrodusmus species showed highest protein (43.6 %), lipid (41.3%) and carbohydrate (47.1%) contents in their dry cell respectively. Thus, Chlorella species (TCO16), Stichococcus species (TC12), Chlamydomonas species (TC12), Ankistrodusmus species (TCO19) and Synechococcus species (TCE14) were the most promising strains for mass cultivation in outdoor raceway ponds in freshwater media for different applications due to their ability to grow well in a liquid medium, high accumulation of protein, lipid and carbohydrates as well as ability to remain in suspension. Further studies shall be undertaken to determine their optimum growth conditions, quality of the biochemical composition and outdoor open pond system. Keywords/Phrases: Growth Rate, Isolation, Lake Tana; Microalgae, Proximate Composition, Screening