The microalga Spirulina have a high nutritional value and due this property it is often used as an ingredient for the develop of food, like ready-to-eat extrudates. In the development of snacks extrudates, physical properties such as expansion index, hardness and bulk density are important for the sensory acceptance. Thus, this study aimed to evaluate the influence of Spirulina sp. LEB 18 on the physical properties of snacks. The raw materials were organic corn flour, organic rice flour and Spirulina biomass. The snacks were extruded on a co-rotating twin-screw extruder. Extrudates were developed with 2.6% Spirulina sp. LEB 18 and without Spirulina sp. LEB 18 (control trial), for comparison purposes. The physical parameters evaluate were expansion index (EI), bulk density (BD), hardness, water absorption index (WAI) and water solubility index (WSI). Statistical evaluation was performed using the Tukey test with a 5% level of significance. The results for snacks added with Spirulina sp. LEB 18 were 4.57±0.09 cm cm-1, 0.077±0.003 g cm-3, 25.43±1.08 N, 8.69±0.65 g g-1 and 29.98±0.68 % for EI, BD, hardness, WAI and WSI, respectively. The sample with microalga did not differed significantly (p <0.05) from the control formulation, with the exception of bulk density. This result can be considered positive, indicating that the increase in microalga content did not affect significantly the hardness and expansion index, which are direct related to the acceptance of this class of food. However the increase of the bulk density is probably due to the high protein content of microalga Spirulina. The hydrophilic proteins tend to compete with the starch by moisture, resulting in less gelatinization. In conclusion, Spirulina can be added in the snacks formulation as a nutritional increase without affect significantly the physical properties (expansion index, hardness, WAI and WSI).