Significance: Irreversible electroporation (IRE) is gaining popularity as a focal ablation modality for the treatment of unresectable tumors. One clinical limitation of IRE is the absence of methods for real-time treatment evaluation, namely actively monitoring the dimensions of the induced lesion. This information is critical to ensure a complete treatment and minimize collateral damage to the surrounding healthy tissue. Goal: In this study, we are taking advantage of the biophysical properties of living tissues to address this critical demand. Methods: Using advanced microfabrication techniques, we have developed an electrical impedance microsensor to collect impedance data along the length of a bipolar IRE probe for treatment verification. For probe characterization and interpretation of the readings, we used potato tuber, which is a suitable platform for IRE experiments without having the complexities of in vivo or ex vivo models. We used the impedance spectra, along with an electrical model of the tissue, to obtain critical parameters such as the conductivity of the tissue before, during, and after completion of treatment. To validate our results, we used a finite element model to simulate the electric field distribution during treatments in each potato. Results: It is shown that electrical impedance spectroscopy could be used as a technique for treatment verification, and when combined with appropriate FEM modeling can determine the lesion dimensions. Conclusions: This technique has the potential to be readily translated for use with other ablation modalities already being used in clinical settings for the treatment of malignancies.