Extraction techniques to obtain bioactive molecules from passion fruit bagasse have emerged recently. The driving force behind this effort lies in the array of biological properties related to its compounds, including anti-carcinogenic, antioxidant, anti-inflammatory, and vasorelaxant properties. Given this background, this work proposes improvements to the extraction process from defatted passion fruit bagasse (DPFB). The effect of pressurized liquid extraction (PLE) temperature was examined at 70, 90, and 110 °C, revealing an increase in global yield and total reducing content (TRC) with rising temperature. However, the yield of piceatannol was statistically equal between 70 and 90 °C and decreased at 110 °C, suggesting thermal degradation. These findings were corroborated by thermal stability analysis and oxygen radical absorbance capacity assessment. The impact of raw material particle size was investigated and showed that granulometric classification led to an increase in the TRC and piceatannol yields by 35% and 84%, respectively, and allowed identifying the piceatannol's location within the outer layer of the passion fruit seed (FR1). Mathematical modelling was applied to the kinetic extraction of DPFB-FR1 to assess the effect of bed height to diameter ratio (H/D). The two-site desorption model has properly fitted experimental data and indicated an enhancement in piceatannol mass transfer rate when increasing H/D. In summary, the present work presents findings and conclusions not previously documented in the literature, contributing to the improvement of PLE and pre-treatment methods for passion fruit bagasse.