<p>A simple and sensitive method using first-derivative ultraviolet spectrophotometry (DS-UV) was developed, validated, and compared to the high performance liquid chromatography (HPLC) method for quantification of paclitaxel (PTX) in a liposomal formulation. Different analytical performance parameters such as linearity, accuracy, precision, specificity, detection, and quantification limits were determined according to International Conference on Harmonization (ICH) guidelines. No interference from the lipid compounds was detected in the HPLC and the DS-UV methods at 246 nm. Linearity determined for paclitaxel concentrations ranging from 6.0 to 24.0 µg mL^-1 presented a correlation coefficient higher than 0.999 for both methods. Relative standard deviation (RSD) values lower than 2% for intra- and inter-day precision data could be obtained. Accuracy mean values ranged from 98.9 to 102.0%. Robustness data showed that the PTX content was unaffected by the alteration proposed. Both methods were adequate to quantify the drug in the liposomal formulation. DS-UV proved to be rapid, accurate, selective, sensitive, and, therefore, an attractive tool for routine determination of PTX.</p>