This study focuses on the chronology of King Den’s reign, the fifth ruler of the 1st Egyptian dynasty. A series of radiocarbon (14C) dates were established on archaeological material from several tombs at the Abu Rawash site, near Cairo, which comprises a complex of 12 monumental mud-brick mastabas. Modeling the 14C results enables us to estimate the date of King’s accession and to link this to the beginning of the 3rd Dynasty, i.e., to Egyptian state’s structuration. Through the application of OxCal software, sets of 14C results obtained from the same archaeological context have been summarized and compared with the precise state of our knowledge on the historical duration of this reign. These results place King Den’s accession between 3104 and 2913 BCE (2σ), with the more likely date being 3011–2921 BCE (1σ). The modeled temporal density thus obtained is based both on new contextualized 14C dates and on an updated reading of the historical information on his reign. This is a dynamic result, which can be refined as soon as we have more data to integrate into the model. Above all, this resulting model becomes a crucial chronological point to better determine the beginning of the Egyptian Old Kingdom.