Terbinafine hydrochloride is a potent antifungal drug indicated for oral and topical treatment of mycoses. A resonance Rayleigh scattering method was developed for the determination of terbinafine hydrochloride through feasible complexation reaction with erythrosine B reagent. In a weak acidic medium (acetate buffer, pH 5.0), terbinafine hydrochloride can react with erythrosine B through virtue of hydrophobic force and electrostatic attraction to form an ion-association complex. The reaction resulted in the appearance of new resonance Rayleigh scattering (RRS) peak at 369 nm. The RRS peak was increased by increasing the concentration of terbinafine hydrochloride in the linear range of 0.1–1.5 µg/mL. All the interaction conditions (erythrosine B concentration, buffer volume, diluting solvent and pH) were optimized. The detection limit was 0.029 µg/mL while the quantitation limit was 0.089 µg/mL. The suggested method after its validation was successfully applied for the determination of terbinafine hydrochloride in different pharmaceutical formulations (tablets and cream) with sufficient recovery.