The aim of this research was to study and compare release characteristics of copper (Cu) in 2 groups of soils from Guilan province in northern (SNI) and Fars province in southern Iran (SSI) with significant differences in Cu availability and other soil properties. The patterns of Cu release from the soils by ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) were studied using 5 kinetic models. Results showed that the power function, simple Elovich, and parabolic diffusion in SSI, and the power function and simple Elovich in SNI, were the best fitted models. The greater rates and magnitude of Cu released from SNI compared with SSI could be interpreted as the greater capability of the former in maintaining Cu concentration in the sufficient range. The difference in Cu release rates was considerable during initial times. Mean initial Cu release rate from SNI was ~3 times higher than that of SSI. The results reveal that the cation exchange capacity (CEC) and pH were the most influential soil factors causing differences in Cu release patterns between these 2 groups of soils. Greater CEC and lower pH in SNI compared with SSI, are mainly responsible for greater initial rates of Cu release in the former. Difference in CEC and pH of these 2 groups of soils was mainly attributed to different soil organic matter, carbonate content, and clay mineralogy.