Background <p>Dengue is an arboviral disease transmitted by <i>Aedes aegypti</i> and <i>Aedes albopictus</i> mosquitoes. Natural plant-based insecticides are promising alternatives to chemical insecticides but face challenges, including rapid degradation of bioactive compounds in aquatic environments. In this study, bioactive plant extracts were encapsulated in water-insoluble CaCO₃ submicron carriers, which are of great interest as targeted drug delivery systems due to their bioadhesive, biocompatible properties, and eco-friendly nature. This approach was applied to achieve the highest efficiency with controlled release of bioactive compounds targeting dengue mosquito larvae.</p> Methods <p>CaCO₃ submicron particles were synthesized using a mixture of Ca(CH₃COO)₂ and NaHCO₃ in H₂O and diethylene glycol as solvents. The combined plant extract of <i>Capsicum frutescens</i> (Naimiris) and <i>Allium sativum</i> (garlic), which showed significant larvicidal activity against dengue mosquito larvae, was encapsulated into CaCO₃ particles, and their release properties and larvicidal activity were examined. The results of the SEM, XRD, XRF, and FTIR analyses confirmed the morphology, structure, and chemical characterization of the CaCO₃ submicron particles. Qualitative phytochemical analysis was also conducted, and the total phenolic and total flavonoid contents were investigated quantitatively.</p> Results <p>The diameter of CaCO₃ particles was 252.3–676.4&#xa0;nm, and the average size was 419.7&#xa0;nm. 85.56 ± 4.65% of plant extract was encapsulated into CaCO₃ particles, and about 27% of the encapsulated product was released to the medium up to 10&#xa0;days. Larvicidal activity showed concentration and time-dependent mortality in mosquito larvae, resulting in up to 55% mortality after 10&#xa0;days for the highest concentration tested.</p> Conclusion <p>The results confirmed that CaCO₃ submicron carriers are effective as slow-release drug delivery systems.</p>