Black soldier fly larvae (BSFL, Hermetia illucens) can valorize food waste into high-value products, including animal feed. However, these food wastes may contain microplastics originating from food packaging eventually compromising the growth and the safety of larvae as feed. This study investigates the impact of polyethylene microplastics size and shape on the growth of BSFL and on the ingestion and egestion kinetics during waste bioconversion. BSFL were reared on artificial food waste containing fruits, vegetables, bread, and dairy products (25% dry matter, single batch of 100 mg/larvae/day) and spiked with spherical or irregular self-produced fluorescently labelled microplastics (26,000 particles/g of substrate). Three size ranges were tested in triplicate for each shape (from 38 to 150 µm) and compared to controls. Throughout the experiment, the larval growth performance was determined and the amount of microplastics in the larval gut was monitored daily (n = 9 per treatment), using fluorescence microscopy. We observed that the presence of microplastics had no impact on larval growth, having a mean maximal larval weight of 221.4 ± 23.3 mg. Further, no bioaccumulation of microplastics (BAF < 0.3 ± 0.1) was observed. However, significant differences in microplastic ingestion were observed based on their size. While a steady increase in microplastics was observed in the larval gut for the smaller particles, the larvae exhibited minimal ingestion of particles surpassing 100 µm. Furthermore, kinetic modelling of the temporal microplastics ingestion and egestion dynamics showed that particle shape can slightly modify the kinetic parameters of ingestion without having any distinct effect on the bioaccumulation. Finally, a 3-day starvation period appeared to be effective in reducing the number of microplastics present in the larval gut by 95.9 ± 4.0 %, but the associated larval weight reduction (30.5 ± 6.6 %) is unfavorable for industrial applications.