The evapotranspiration () process is an essential component in many agricultural water management systems, and its estimation is even more determinant when crops are grown under water-limited environments. The traditional canopy resistance () approaches were evaluated to simulate potato evapotranspiration () using the original Penman–Monteith equation under different irrigation levels. A field study was carried out on a drip-irrigated potato crop (var. Puyehue INIA) located in the Research Center Carillanca (INIA), La Araucanía Region, Chile (38°41′ S, 72°24′ W, 188 m above sea level) during the 2018/2019 and 2019/2020 growing seasons. The different irrigation levels were full irrigation (), 75% of (), and 60% of (). The soil water content, morphological, physiological, meteorological, and micrometeorological variables were measured to calculate the different approaches and estimate ET for both growing evaluated seasons. The final values of estimated were compared to the soil water balance method (). The use of amphistomatous (LA) and hypostomatous (LH) approaches are the best alternative to estimate the on potato crops. The best estimation of ET was found for with an overestimation of 0.6% for , 7.0% for , and 13.0% for , while for with underestimations of 12.0, 11.0 and 31.0% for , , and , respectively. The lowest average values of root mean square error (RMSE), mean absolute error (MAE), and index of agreement (d) were observed for in both and conditions, with values of 4.4 and 3.2 mm, 3.2 and 2.5 mm, and 0.82 and 0.87, respectively. More investigation is necessary on the plasticity of the morphological features of potato leaves and canopy geometry, as the stomatal water vapor flowing on the canopy surface could be affected, which is a key factor in the canopy resistance model for accurate estimation under soil-water-limited conditions.