In this study, response surface methodology (RSM) was employed to optimize the ingredient formulation and processing parameters of Spirulina platensis incorporated soy yogurt production such as temperature, time, and amount of Spirulina platensis on the sensory evaluation responses on 9 point Hedonic rating. Besides, the physico–chemical properties such as pH, titratable acidity, viscosity and penetration of the Spirulina platensis incorporated soy yogurt were also analysed. The analyses show that the Spirulina platensis incorporated soy yogurts have a pH from 3.43 to 5.55, acidity from 0.64 to 2.32 (%), Brookfield viscosity from 752 to 903 Centipoise and penetration from 362 to 432 1/10th mm at 25°C during the optimization process. From the analysis of variance, the R2 of all response variables is more than 0.77 that indicates that a high proportion of variability was explained by the model. Based on the response surface 3D plot of the sensory evaluation, the optimum acceptability of the Spirulina platensis incorporated soy yogurt processing parameter are at temperature of 40°C, 12 h of the fermentation duration and 0.80% (w/w) of the Spirulina platensis.