Display omitted •Chlorella vulgaris was tolerant to levofloxacin, and could withstand its high doses.•96h EC50 of levofloxacin for C. vulgaris was 58.6mgL−1.•The acclimation of C. vulgaris enhanced the removal of levofloxacin.•Sodium chloride stimulated the biodegradation of levofloxacin up to 91%.•NaCl (1%w/v) increased the degradation rate constant (k) of LEV from 0.011 to 0.257d−1. The extensive contamination of levofloxacin (LEV) in aquatic ecosystems has attracted increasing attention because of the potential for development of bacterial resistance and its eco-toxicity to non-target organisms. Biodegradation of LEV was significantly improved upon the acclimation of a freshwater microalga, Chlorella vulgaris and in the presence of elevated salinity. Among the six wild species (Chlamydomonas mexicana, Chlamydomonas pitschmannii, Chlorella vulgaris, Ourococcus multisporus, Micractinium resseri, Tribonema aequale), C. vulgaris showed the highest removal capacity (12%) of LEV at 1mgL−1. The acclimated C. vulgaris, which was pre-exposed to 200mgL−1 of LEV for 11days, exhibited enhanced removal of 1mgLEVL−1 by 16% after 11days of cultivation. The addition of 1% (w/v) sodium chloride into the microalgal media significantly improved LEV removal by >80% in the C. vulgaris culture. The bioaccumulation of LEV at day 11 in C. vulgaris cells without NaCl was 34μgg−1, which was elevated to 101μgg−1LEV at 1% NaCl. The bioconcentration factor for LEV was 34 and 1004 in 0 and 1% NaCl, respectively. The mass balance analysis of LEV showed that more than 90% of LEV was biodegraded by C. vulgaris at day 11 with the addition of 1% NaCl. These results demonstrated that the enhanced removal of LEV by salinity was mainly through bioaccumulation and subsequent intracellular biodegradation by C. vulgaris cells.