This paper reports the application of a carbon paste electrode modified with magnetite nanoparticles and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate in the electroanalytical determination of 17β-estradiol and estriol. These estrogens are potential endocrine disruptors and thus it is relevant the development of devices for their monitoring. Transmission electron microscopy, scanning electron microscopy and zeta potential techniques were applied to characterization of the modifier materials. In cyclic voltammetry experiments, irreversible oxidation peaks were observed for 17β-estradiol and estriol at +0.320 V and +0.400 V, respectively. The anodic currents obtained were approximately three times greater than those provided by the unmodified electrode due to the presence of magnetic nanoparticles and the ionic liquid, which improved the sensitivity of modified electrode. For the analysis, the parameters of the square-wave voltammetry (scan increment, amplitude and frequency) were optimized by Box-Behnken factorial design for each estrogen. For 17β-estradiol in B-R buffer pH 12.0, the calibration plot was linear from 0.10 to 1.0 μmol L-1, with a detection limit of 50.0 nmol L-1. For estriol in B-R buffer pH 11.0, the linear range was 1.0 to 10.0 μmol L-1, with a detection limit of 300.0 nmol L-1. The modified electrode was applied in the determination of 17β-estradiol and estriol in pharmaceutical formulations and the results were comparable to those obtained using UV/VIS spectrometry. Statistical tests were applied to evaluate the results and it was concluded that there was no significant difference regarding the precision and accuracy of the data provided by the two methods.