In autumn 2014, sewer construction works in one of the busiest parts of Tehran yielded Islamic pottery sherds from the Safavid to Qajar periods. Following a visit by archaeologists from the Iranian Centre for Archaeological Research, one of the authors (MEEJ) was appointed as the director of salvage excavations at archaeologically sensitive locations along the sewer line that had provided evidence such as potsherds, glass fragments, metal pieces and bricks. We opened six small trenches along the line of sewer construction, of which, Trenches I and VI proved to be more important the others due to the finds they yielded. These find, based on comparable specimens, can be dated to the fifth millennium BC or even earlier, Late Neolithic. In fact, Tehran for its favorable environmental conditions is one of the best areas to host Chalcolithic sites. The results of Moulavi excavations provided significant information about the prehistoric cultures of the Iranian Central Plateau, especially Chalcolithic cultures. The archaeological finds of the Trench I include potsherds of Cheshmeh Ali culture, animal bones, lithics such as blades, bladelets and bullet-shaped core, a possible hearth and a human burial; all these finds indicate sporadic settlement of the early Chalcolithic period in the Tehran Plain. The results of analyzed specimens from this trench confirm the existence of an occupation from the sixth to the first millennium at this spot. In this paper we describe and discuss the results of Trench I.