Central Asia is considered one of the key regions as a potential supplier of Bronze Age tin and thus – at least part of – the answer to the question of the "tin mystery". Large tin ore deposits are known from Afghanistan, Uzbekistan, Tajikistan as well as Kazakhstan, and compared to other tin-bearing provinces such as Cornwall/Devon, the Erzgebirge or the Iberian Peninsula, mining archaeological evidence for ancient tin ore mining is abundant. This is certainly due to the fact that underground mining was common, whereas in the other regions mining of alluvial deposits may have been predominant. However, what was lacking until recently was archaeological evidence of ore smelting and, moreover, analytical evidence of how the ores impacted on local and supra-regional bronze metallurgy. Here we present the results of the study of a unique bronze slag from near the Mušiston tin-copper deposit in Tajikistan with microscopic, mineralogical, chemical and isotopic analysis. According to the results, the slag has unusual mineralogical characteristics and can be clearly associated with the nearby deposit on the basis of chemistry and isotopy. This is thus the first time that a slag from a tin smelting process can be used to trace the tin/bronze metal produced back to its ore source. Building on this important result, we also present first data of bronze artefacts from Central Asia to provide a preliminary assessment of the importance of the Mušiston ores for bronze metallurgy.