In this work microfiber mats of Nile tilapia (Oreochromis niloticus) gelatin were successfully fabricated by using Solution Blow Spinning technique. The concentration and viscosity of fish gelatin solution, in acid acetic/water (80% v/v), were correleted to the morphology and diameter of the gelatin microfibers. It was found that increased solution viscosity leads to increase of fibers diameters from approximately 280 nm at viscosity ~ 0.085 Pa.s. to approximately 1195 nm at viscosity ~ 1.877 Pa.s. The TG thermograms showed similar thermal profiles for all fibrous mat gelatins with thermal stability at temperatures below 180°C. The DSC curve showed two endothermic peaks being the second one, in the range of 100-130°C, strongly influenced by the microfiber diameters. It shifts to higher temperature increasing the microfiber diameter. This behavior was associated to the diffusion of water in the microfibers. Combined DSC/TG results showed a significant influence of the microfiber diameter on the water absorption and desorption process.