In this paper, we explore the validity of rank‐size rule in the Moroccan urban system. We use data from the 1982, 1994, and 2004 censuses. Three thresholds are considered to truncate the data: 5000, 50000, and 100000 residents. Power law states that the rank (r) of a city is proportional to a power of its size (Sr), that is, r ̴ S•α. The ordinary least squares (OLS) method is used to estimate α. Using OLS method without Gabaix‐Ibragimov correction (GIC) provides evidence of the validity of Zipf's law for cities of more than 100 000 dwellers.When the GIC is used, it appears that the zipfian distribution (α = ‐1) is also valid for cities of more than 50000 inhabitants. Over the period 1982–2004, it seems likely that intermediate cities grew more rapidly than other cities. This may lead to a more balanced distribution of the Moroccan urban system.