Hydrocolloids are the most used thickener agent in the food industry for improving the texture and stability of emulsion-based products. However, hydrocolloids affect the structure of the food matrices modifying their sensory properties. Thus, this work aimed to study the effect of particle size and type of thickener agent on in vitro oral processing and sensory perception of emulsion-based desserts. Oil-in-water emulsion-based desserts containing avocado oil (5%) as lipid phase, cacao powder (5%), and vanilla (1.6%) as flavorings, and stevia as sweetener (0.12%) were prepared. Emulsion-based desserts were studied at different particle sizes (nanoemulsions: nanoscale and conventional emulsions: microscale) and thickener types (starch and xanthan gum). In vitro oral processing was performed in a rotational rheometer, where viscosity values were registered during 30 s while shearing the sample in the presence of human saliva (1:4 saliva:sample) at a constant shear rate of 50 s-1. Sensory evaluation by multiple paired comparison test was carried out, where 50 panelists were asked about of intensity of different attributes: aroma, flavor, sweetness, consistency, and creaminess. The viscosity curves obtained showed a decay of apparent viscosity values with the shearing time, which was more pronounced in the samples containing starch due to the breakdown of starch granules by shearing and saliva activity. Regarding sensory evaluation, significance differences among emulsion-based desserts were obtained in all attributes evaluated (Friedman statistical analysis, α=0.05). Xanthan gum-based desserts were more consistent and creamier than starch-based ones, but the starch desserts had a greater flavor intensity. In addition, nanoemulsions were perceived with a greater odor intensity and a lesser sweetness than conventional emulsions. In conclusion, the structural breakdown of emulsion-based matrices under oral conditions depends on hydrocolloid type and particle size, affecting their sensory properties. Therefore, using xanthan gum and nanoemulsions decreases desserts' structure breakdown, increasing perceived consistency and creaminess.