Pirfenidone (PRF) is a synthetic compound used to treat idiopathic pulmonary fibrosis, but its oral administration may cause systemic side effects. This study aimed to develop and validate a bioanalytical method to quantify PRF and evaluate the pharmacokinetic and biodistribution profile of PRF-loaded solid lipid nanoparticles (SLNs) delivered via the pulmonary route. A high-performance liquid chromatography (HPLC) method was validated following the Food and Drug Administration (FDA) guidelines, showing acceptable selectivity, accuracy, precision, and stability in plasma and lung tissue. PRF SLNs were prepared by solvent injection and had a mean particle size of 240.3±3.57 nm and a polydispersity index of 0.386–0.392. Intratracheal administration of PRF SLNs resulted in higher maximum concentration and Area Under the Curve (AUC) values than oral PRF. Biodistribution studies showed that PRF SLNs achieved approximately fivefold greater AUC in lung tissue than free PRF, with lower distribution in the liver and kidneys. These findings indicate that pulmonary PRF SLNs enhance lung targeting and may reduce systemic exposure, while the validated HPLC method supports reliable pharmacokinetic and tissue distribution analysis.