The processing of cobalt-bearing ores from the Dashkesan deposit was studied using a two-stage roasting process aimed at destroying the cobaltite crystal lattice. Hydrometallurgical treatment of cobalt–arsenide ores by alkaline leaching was also investigated. The ore contains a significant amount of arsenic, which represents a serious challenge because it hinders cobalt extraction into solution. Numerous studies have been conducted in this direction. To separate arsenic, roasting with the addition of soda at 700–750°C was performed. Experimental results showed that, in the absence of soda, approximately 90% of arsenic transferred into solution during subsequent leaching. The water solubility of the sinter obtained at 700°C was examined. Hydrometallurgical treatment was carried out in alkaline solutions to minimize the loss of valuable metals. During the two-stage leaching process, arsenic extraction into solution reached 98%. Arsenic was removed from the solutions with an efficiency of 85–90% in the form of trisodium arsenate (Na₃AsO₄) and calcium arsenate (Ca₃(AsO₄)₂).