Cadmium is one of the valuable metals in the oxidic and sulfidic ores of zinc, which is separated as a solid slag namely cold filter cake from the zinc effluent. This metal has several applications in the strategic industries. The purpose of this study was the separation of cadmium from zinc using solvent extraction process. The potential of ultrasonic waves to improve the rate and selectivity of the Cadmium extraction was evaluated and compared to the conventional method by mechanical stirrer. First of all, the filter cake was obtained from Isfahan Zinc Smelting Company (IZSC) and its chemical characterization was analyzed. Then, primarily leaching experiments were performed in the presence of 20% pulp concentration, temperature of 60°C, 20% (v/v) sulfuric acid for 2 hours. Results of leaching experiments showed that the recovery values of zinc and cadmium are 93% and 88%, respectively. In the next step, the solvent extraction experiments were performed using 20% (v/v) D2EHPA diluted in kerosene at ambient temperature and organic to aqueous phase ratio (O/A,1:1 ) using both mechanical stirrer and ultrasonic methods. The experiments of mechanical stirring were conducted at stirring rate of 550 rpm for 10 min in the different values of pH (1, 2, 3, and 4). The experiments of ultrasonic stirring were carried out in 3 min, different values of pH and ultrasound power 30 Watt. Desired zinc extraction (higher than 50%) and undesired cadmium extraction in both mechanical and ultrasonic stirring systems were obtained for the leachate of filter cake. To investigate the conditions of cadmium extraction, synthetic sulfate solutions of cadmium and zinc were simulated and used. Then, effects of type of the stirring system, the ratio of zinc and cadmium metals, pH value, contact time of two phases, and ultrasound power on the separation of metals were investigated. The results showed that using the ultrasonic stirring system increased the extraction efficiency of cadmium (20%) and reduced the extraction time to 1 min towards the mechanical stirring system, however zinc extraction had not significant improvement using the ultrasonic stirring compare to mechanical system. Furthermore, it is observed that in the mechanical and ultrasonic stirring systems, the highest rate of extraction of two metals occur in the pH values of 4 and 1, respectively. The results indicated that by increasing the ultrasound power to 60 watt, the extraction rate of cadmium was increased and in the higher power values the emulsion formation was prevented the phase disengagement. According to the results, despite of increasing cadmium extraction using the ultrasonic system, zinc extraction was higher than cadmium under different conditions. Therefore in the environments where the values of zinc metal were high, using D2EHPA extractant is not appropriate for cadmium extraction and it is suggested that the zinc was extracted by solvent extraction route follow by cadmium extraction by the other rotes such as cementation and vacuum distillation. Key words : Solvent extraction, ultrasonic, cadmium, zinc, D2EHPA