In this study, tebuconazole (TEB)-loaded poly-3-hydroxybutyrate (P3HB)-based microparticles were developed and comprehensively characterized. TEB-loaded microparticles (10, 25, and 50%) were prepared using double emulsification technique. Encapsulation efficiency of TEB varied from 59 to 86%. As the loading amount was increased, the average diameter of microparticles increased too, from 41.3 to 71.7 µm, while zeta potential was not influenced by TEB loading, varying between -32.6 and -35.7 mV. TEB was released gradually from 10, 25, and 50% loaded particles, and over 60 days, 25, 43, and 38%, respectively, of the initially loaded amount was released. The data obtained from in vitro TEB release were fitted to different mathematical models. It was shown that the release profiles of TEB could be best explained by Zero-order, Higuchi models and Hixson-Crowell. The antifungal activity of the P3HB/TEB microparticles against phytopathogenic fungi F. moniliforme and F. solani was comparable to that of the free fungicide. Thus, hydrophobic agrochemicals (TEB) can be effectively encapsulated into P3HB microparticles to construct slow-release formulations.