Amiantis purpurata is a common warm-temperate water bivalve species distributed from southern Brazil to northern Patagonia, Argentina, which has a rich and well preserved fossil record in the San Matías Gulf (SMG) dating back to the late Quaternary. This study aims to establish A. purpurata shells as a new palaeoarchive of past marine conditions in South America. We compared the stable oxygen and carbon profiles (δ18Oshell; δ13Cshell) of eleven specimens of A. purpurata from different geological times (modern, Late Holocene and interglacial Late Pleistocene), and additionally present in situ oxygen isotope values of seawater within SMG (δ18Owater). Using both sets of information, we calculated and reconstructed palaeowater temperatures for the Late Holocene and compared them to modern water temperatures. Our findings indicate that A. purpurata records past environmental parameters such as water temperatures on a seasonal scale and can therefore be considered a suitable candidate for future palaeoenvironmental reconstructions in Northern Patagonia. This study is the first step towards further stable isotope analyses on fossil A. purpurata shells, which will show whether and if so, to what extent, important global climate events such as the Neoglacial (Early Holocene), the Hypsithermal (Middle Holocene) and the Little Ice Age (Late Holocene) occurred in South America.