The study investigates the ability of artificial neural networks (ANN) with artificial bee colony (ABC) algorithm in daily reference evapotranspiration (ET0) modeling. The daily climatic data, solar radiation, air temperature, relative humidity, and wind speed from two stations, Pomona and Santa Monica, in Los Angeles, USA, are used as inputs to the ANN-ABC model so as to estimate ET0 obtained using the FAO-56 Penman-Monteith (PM) equation. In the first part of the study, the accuracy of ANN-ABC models is compared with those of the ANN models trained with Levenberg-Marquardt (LM) and standard back-propagation (SBP) algorithms and those of the following empirical models: The California Irrigation Management System (CIMIS) Penman, Hargreaves, and Ritchie methods. The mean square error (MSE), mean absolute error (MAE) and determination coefficient (R 2) statistics are used for evaluating the accuracy of the models. Based on the comparison results, the ANN-ABC and ANN-LM models are found to be superior alternative to the ANN-SBP models. In the second part of the study, the potential of the ANN-ABC, ANN-LM, and ANN-SBP models in estimation ET0 using nearby station data is investigated.