Trastuzumab‐loaded ethosomes were developed and characterized to enhance transdermal delivery and provide controlled drug release. Eight formulations containing varying concentrations of lipid were prepared and evaluated for Preformulation parameters, vesicle characteristics, in vitro release behavior and stability. Trastuzumab was identified as a white to off-white, tasteless and odorless crystalline powder with a melting point of 70–80 °C and good aqueous solubility. FT-IR studies confirmed the absence of drug–excipient interactions. The ethosomal vesicles exhibited spherical morphology with particle sizes ranging from 186 nm to 253 nm and a negative zeta potential (–23 mV to –30 mV), indicating good colloidal stability. Entrapment efficiency was high (76.86 %–85.10 %), with formulation F8 showing the highest value and achieving 97.98 % cumulative drug release within 12 h. Drug-release kinetics for the optimized formulation followed Higuchi’s diffusion model (R² = 0.973). Accelerated stability testing (40 ± 2 °C/75 ± 5 % RH for 3 months) revealed no significant loss of drug content, which remained above 94 %. The results demonstrate that ethosomes can effectively encapsulate trastuzumab and provide a stable, sustained-release transdermal delivery system suitable for further therapeutic development. Keywords: Trastuzumab, Ethosomes, FTIR Studies, In vitro drug release studies, Stability studies