This paper presents for the first time the study of electrochemical behavior of well known immunosuppressant drug - rapamycin (sirolimus) using boron-doped diamond electrode. Rapamycin provided single and oval-shaped oxidation peak at +1.1 V vs.Ag/AgCl electrode in Britton-Robinson buffer solution at pH 3 confirming highly irreversible behavior of analyte at boron-doped diamond electrode. A differential pulse voltammetry was used for quantification of tested drug under the optimum experimental conditions. The calibration curve was linear over the range from 0.5 to 19.5 mu M (R-2 = 0.9976) with detection limit of 0.22 mu M. Repeatability of ten successfully measurements of three different concentrations (5,10 and 15 mu M) was 2.5, 1.9 and 1.7%, respectively. Influence of most common biomolecules presented in urine samples was evaluated. The suggested analytical methodology was successfully applied for determination of rapamycin in four urine samples with excellent recoveries. The developed approach could be beneficial in analysis of rapamycin in biological samples using boron-doped diamond electrode as up-to-date electrochemical sensor and could represent inexpensive analytical alternative to separation methods. (C) 2015 Elsevier Ltd. All rights reserved.