In this study, the trend of overwintering and breeding populations of the endangered white-headed duck Oxyura leucocephala was studied using 52 years of mid-winter waterbirds census in Iran (1969–2020) and breeding reports of the species in the 2010s. The trend of species population changes was calculated using RTRIM statistical package in R software. Species population in Iran indicates a substantial increase of 21.3% per year and a moderate increase of 4.4% per year over the last ten years. The results showed that the average annual total population of white-headed duck, overwintering in Iran, was 470.4 ± 126.3 over the past 44 years, covering 14 provinces and 45 wetlands. On average, 41.6% of the population was in Mazandaran province, 25.1% in Fars province, 18.6% in Golestan province, 4.4% in Khuzestan province, and 10.3% in other provinces. The breeding population of white-headed duck in Iran was estimated between 103 and 301 pairs, showing that the breeding population of the species in Iran has increased compared to the past decades. In order to protect this species, it is appropriate to develop a coherent and species-oriented action plan based on the climatic and geographical conditions of the wetland habitats of the species at the national level.