Creatinine is an important biomarker of kidney diseases. In this work, a fast and facile electrochemical sensor was developed for creatinine detection based on the use of copper nanoparticle-modified screen-printed electrodes. The copper electrodes were prepared by simple electrodeposition of Cu (aq). The electrochemically inactive creatinine was detected reductively via the in situ formation of copper-creatinine complexes. Two linear detection ranges, 0.28-3.0 mM and 3.0-20.0 mM, were achieved using differential pulse voltammetry, with the sensitivities of 0.824 ± 0.053 μA mM and 0.132 ± 0.003 μA mM, respectively. The limit of detection was determined to be 0.084 mM. The sensor was validated in synthetic urine samples to yield 99.3% recovery (%RSD = 2.8), demonstrating high tolerance to possible interfering species. Finally, the stability of creatinine and its degradation kinetics at different temperatures were evaluated using our developed sensor. The loss of creatinine was found to be a first-order reaction with the activation energy of 64.7 kJ mol.