The diversity and abundance of bees associated with alfalfa and onion fields in Mashhad and Chenaran were evaluated from mid June until late October 2010. Considering the type and flowering period of the studied crops, by using a standard sweeping net, either a weekly or biweekly sampling program of apoid bees were carried out in selected fields for both crops. As a result, 17 species of 15 genera belonging to 6 families of super family Apoidea were identified. Among the identified species Anthidium diadema (Latreille1809) is a new species recorded for Iran while 7 genera and 5 species reported for the first time for Razavi Khorasan province. The species, Anthidium florentinum with relative abundances of 29.16% and 28.14% in Mashhad and Chenaran respectively were the dominant bee in alfalfa, and in onion fields, the genus Andrena sp. with relative abundance of 30 % in Mashhad and 42.2% in Chenaran was recognized as the dominant bees. Statistically, both the effects of crop type and site of study as well as the interaction of crop × site on Shannon-Wiener index of biodiversity were significant. The value of this index for alfalfa was the highest in Mashhad (1.92) and lowest in Chenaran (1.78). The Sorenson index of similarity between bees community of alfalfa in Mashhad and Chenaran, onion of Mashhad and Chenaran and between alfalfa and onion were respectively 0.81, 0.60 and 0.54, indicating a high similarity between apoid fauna of alfalfa fields in the two different regions. Considering the importance of the functions of biodiversity of insect pollinators in agroecosystems, for protection and as well for its optimum utilization, extensive understanding of the characteristics, temporal and spatial distribution of its affecting components, namely pollinator wasps is required emphatically.