Novel cellulose acetate (CA) nanofibers incorporated with hormone progesterone (P4) were prepared by electrospinning and its potential as a controlled release system for medicine and veterinary was evaluated by controlled release essay. The morphology, thermal behavior, and structure of P4‐loaded CA nanofibers were characterized by scanning electron microscopy, differential scanning calorimetry, and Fourier‐transform infrared spectroscopy. The analyses revealed that the incorporation of P4 increased nanofibers' diameter from around 340 to 892 nm to 8% w/w P4‐loaded CA nanofibers. Furthermore, P4 has demonstrated high interaction with CA affecting its crystalline structure, since pure CA nanofibers presented 67.23% of crystallinity while P4‐loaded CA nanofibers where amorphous. Ultimately, the drug release essay demonstrated a two‐stage profile, and regarding release kinetics, the samples evidenced a diffusion mechanism depending on P4 concentration in the nanofiber.