Fucoxanthin is a carotenoid that exerts multiple beneficial effects on human health. However, reports comparing microalgae culture conditions and their effect on growth and fucoxanthin production are still limited . Isochrysis galbana and Phaeodactylum tricornutum cultures in different light (62.0, 25.9, 13.5, or 9.1 μmol photons m -2  s -1 ), mixing conditions (1 vvm aeration or 130 rpm agitation), and media compositions (F/2 and Conway medium) were studied for comparison of cellular growth and fucoxanthin production on F/2 medium. I. galbana showed a better adaptation to tested culture conditions in comparison with P. tricornutum , reaching 2.15 × 10 7  ± 4.07 × 10 6  cells mL -1 and a specific growth rate (μ) of 1.12 ± 0.05 day -1 under aerated conditions and 62.0 μmol photons m -2  s -1 light intensity. Fucoxanthin concentration was about 25 % higher in P. tricornutum cultures under 13.5 μmol photons m -2  s -1 light intensity and aerated conditions, but the highest fucoxanthin total production was higher in I. galbana , where 3.32 mg can be obtained from 1 L batch cultures at the 16th day under these conditions. Moreover, higher cell densities (~32.41 %), fucoxanthin concentration (~42.46 %), and total production (~50.68 %) were observed in I. galbana cultures grown in Conway medium, if compared with cultures grown in F/2 medium. The results show that the best growth conditions did not result in the best fucoxanthin production for either microalgae, implying that there is not a direct relationship between cellular growth and fucoxanthin production. Moreover, the results suggest that I. galbana cultures on Conway medium are strong candidates for fucoxanthin production, where 1.2 to 15 times higher fucoxanthin concentration are observed in comparison to macroalgal sources.