Background: Amaranthus pollen grains are known to be highly allergenic and a potential cause of respiratory allergic diseases. Nevertheless, data on the prevalence of Amaranthus pollen in the environment is limited and almost non-existent for Saudi Arabia. Methods: We conducted an investigation to record the airborne incidence of A. viridis and other allergenic pollen in Al-Khobar, Dammam, Hail, Jeddah, Jizan, Qassim and Taif, using Burkard Volumetric Samplers. The samplers were operated continuously for one year at each location. Results: The data revealed A. viridis as one of the major components of outdoor airspora, constituting a maximum of 96% of total pollen counts in Hail, followed by Al-Khobar (89%), Jeddah (87%), Qassim (85%), Taif (84%), Dammam (83%) and Jizan (61%). These higher percentages contributed largely to the total weed pollen catch during August to November in all seven regions. In addition, the data also showed that A. viridis pollen were present throughout the year with distinct seasonal variations. The diel periodicities for at least five sites averaged over a year showed mid-day to early evening maxima. The maximum concentration approached 3000/m 3 of air in October and 1827/m 3 of air in September. The data also exhibited a seasonal pattern in their maximum appearance. Conclusion: Further studies related to biochemical and allergological aspects are needed to confirm the allergenic impact of Amaranthus pollen and sensitization in allergic individuals in the Kingdom of Saudi Arabia.