Abstract This study was undertaken to investigate the dehydration characteristics of the cyanobacterium Aphanothece microscopica Nageli in a convective hot-air dryer. The dehydration characteristics of the biomass were examined at air temperatures of 40, 50 and 60 °C and sample thicknesses of 3, 5 and 7 mm. During the dehydration experiments, air velocity was held stable at 1.5 m/s (parallel flow). The effects of air temperature and sample thickness on the dehydration characteristics and quality parameters (instrumental colour and chlorophyll a) of the dehydrated biomass were determined. The transport of water during dehydration was described by Fick's equation and effective diffusivity was between 8.1 × 10−8 and 18.8 × 10−8 m2 s−1. The experimental dehydration data on biomass obtained were fitted to the Henderson and Pabis model, and the drying rate constant was between 0.005 and 0.024 min−1. The response surface methodology was very efficient in determining product quality, showing the strong effect of temperature on instrumental colour and chlorophyll a content. The thicknesses evaluated showed a less significant effect on the final quality.