Different types of metal-bearing wastes, such as WEEE (Waste Electrical and Electronic Equipment), are important urban minerals in modern society, and the efficient recycling and reuse of their metal values is of key interest. Pyrometallurgical copper smelting is one of the most prominent ways of treating WEEE, however, more accurate experimental data is needed regarding the behavior of different elements during each process stage. This article investigates the behavior of tin and antimony, both commonly present as trace elements in electrical and electronic waste, in secondary (i.e., sulfur-free) copper smelting conditions. The experiments were conducted in oxygen partial pressure range of 10 −10 –10 −5 atm, covering the different process steps in copper smelting. The basis of the equilibrium system was metallic copper–iron silicate slag, with the addition of alumina and potassium oxide to account for the presence of these compounds in the actual industrial process. The results showed that the distribution coefficients of both trace metals, L Cu/slag = [wt % Me] copper /(wt % Me) slag , increased significantly as a function of decreasing oxygen pressure, and the addition of basic potassium oxide also had an increasing effect on the distribution coefficient. A brief comparison between EPMA and LA-ICP-MS (electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry), the two in situ analytical techniques used, was also presented and discussed.