Aim: To investigate the transcription of selected antioxidants and relevant genes under varying temperature conditions, and to identify the optimum temperature for antioxidants production by A. platensis. Methods and Results: The dry weight (DW), pigment production, antioxidants production and gene transcription were examined in A. platensis growing under three temperatures of 23, 30, and 37°C. The cyanobacterial DW was highest in the high temperatures (30 and 37°C), while the pigments; Chl a, carotenoids, C-phycocyanin and total phycobiliprotein (PBP) contents showed their maximum value at 30°C. The total soluble protein and carbohydrate contents were highest at 30°C. Lipid peroxidation, as a marker for thermal stress, was high at 23°C, while higher temperatures remarkably reduced lipid peroxidation levels. Antioxidants activity was increased by 1.5-fold at 30°C and temperature fluctuations induced the antioxidant enzyme activities. The transcriptional abundance of heat shock protein (HSP90), glutamate synthase (GOGAT), delta-9 desaturase (desC), iron-superoxide dismutase (FeSOD), and the large subunit of Rubisco (rbcL) genes was measured under the same temperatures.