Observation of temperature effect on the chlorophyll content of eight (8) filamentous cyanobacteria strains isolated from hot springs in Indonesia had been done. The study aimed to determine the maximum temperature to the growth of the eight cyanobacteria strains, i.e. strain of HS-4, HS-10, HS-16, HS-30A, HS-31A, HS-34, HS-40A and HS-41. The eight strains isolated from five (5) hot spring in West Java, i.e. Ciseeng, Rawa Danau Banten, Pancar Mountain, Maribaya, and Ciater. Incubation temperatures were 20 °C, 30 °C, 35 °C, and 50 °C, while the parameters were chlorophyll content. Observations were made over a period of approximately 44 days. The results of the study during the 44 days of observation showed chlorophyll content of the strains decreased from day 3 to day 37 drastically, and then increased at day 44. During 37 days of observation, those strains are likely to experience the adaptation phase of growth. From this study, it could be seen that the strains of cyanobacteria from hot springs could be cultured only at temperatures below the temperature of its habitat, which is at a temperature of mesophyll. In addition, one strain that survived at 50 °C was found, i.e. the HS-16 strain (PAN003) originating from a habitat with a temperature of ±69 °C (Red Crater on Pancar Mountain). Those hot spring cyanobacteria strains are the thermotolerant strains.