Field studies were carried out in a field belonging to Economic Entomology Department, Faculty of Agriculture, Mansoura University during the two successive seasons 1998/99 and 1999/2000 on sweet pea (Pisum sativum L.), to study the population density of piercing sucking insects attacking this crop and the effect of certain weather factors on the population density of these insect pests. The results indicated the presence of eight piercing sucking insect species infesting sweet pea. These species are namely ; Aphis craccivora Koch, Empoasca lybica DeBerg, Achrosiphum pisum Harr., Empoasca descipiens Paoli, Bemisia tabaci Genn., Thrips tabaci Lind., Nezara viridula L. and Lygus hesperus. The dominant species among them was A. craccivora (36.67 and 39.92% from the total catch) in the two seasons, respectively. Nine predators were also found inhabiting sweet pea, namely; Coccinella undecimpunctata L., Cydonia vicina isis Gr., Cydonia vicina nilotica Muls, Scymnus syriacus, Paederus alferii Koch, Metasyrphus corollae F., Paragus compeditus, Chrysoperla carnea (Steph) and Orius albidipennis (Reut.), while there were three aphid parasitoid found in sweet pea namely; Diaeretiella rapae (M'Intosh), Trioxys angelicae (Haliday) and Aphidius sp. The dominant predator  species among them was O. albidipennis and its ratio was 29.83 and 30.62% during the two seasons of study. The result showed that A. craccivora and A. pisum started to appear in the third week of December during the two seasons of study, then the population during of these species increased gradually and reached its maximum during the first  and second week of March, during the two seasons of study. Also, the results recorded four peaks for E. lybica and E. discipiens in each season of study. B. tabaci  had five peaks in sweet pea in 1998/99 season, while it was three peaks in 1999/2000 season. T. tabaci and L. hesperus had three peaks during the two seasons of study. The results cleared that temperature and relative humidity affect the catch of the piercing sucking insect species in the two seasons of study, and their combined effect was higher.