This paper discusses the Paleolithic and Mesolithic periods in Istria. These prehistoric periods are known to us through a large number of archeological sites where evidence of the presence of a prehistoric man has been found. The Paleolithic period begins approximately 2.5 million years ago, and the main features of the period are man's discovery of tools, hunting, fishing and the nomadic way of life. The Paleolithic period is followed by the Mesolithic period, which began approximately 10,500 years ago, and is characterized by the adaptation of hunter-gatherers to the major changes in climate and environment that occurred at the end of the Ice Age. Although a large number of archaeological sites in Istria contain traces of the above mentioned periods, in terms of their abundance and richness, it is worth pointing out the sites of Šandalja, Romualdova pećina, Pupićina peć and Polje Čepić. The rich stratigraphy of Šandalja II provides a large amount of data on the Upper Paleolithic and analyzes of lithic material provided the information about the intensity of the population, movement and lifestyle of the Paleolithic man. The Romualdova pećina is one of the most important sites in the area of Istria with the remains of Mousterian culture, but it certainly remains noticeable after the discovery of the Upper Paleolithic cave paintings. The Late Pleistocene period can clearly be traced through the site of the Pupićina peć, which, judging by the amount of lithic material, represented a place for long-term residence and seasonal habitat of prehistoric hunter-gatherers. Until recently, Mesolithic open-air sites were rare in the Istrian area, but through the archeological survey of the Polje Čepić, 5 Mesolithic sites were discovered - Kralji, Žiganti, Marišće and Kostadini, which provided evidence of the presence of Mesolithic communities in the Istria. Considering the current state of exploration, there is a noticeable increase in the number of Mesolithic sites compared to the Paleolithic ones. Climate and environmental change associated with the last glacial maximum can be considered as one of the possible causes.