Haemonchosis caused by Haemonchus contortus is highly pathogenic and economically important parasitic infection of small ruminants causes production loss, retarded growth and even mortality in young animals. Across-sectional study was conducted in sheep slaughtered at Jimma municipal abattoir, south west Ethiopia from November 2016 to April 2017, to estimate the prevalence and associated risk factors of haemonchosis. Post mortem examination of the abomasum of sheep was performed according to the standard procedures for identification of adult H. contortus. Of the total 384 slaughtered and examined sheep, (48.7%) were found infected with H. contortus. The prevalence of haemonchosis in this study was significantly higher (P= 0.035) in sheep with young age, 54.3% (OR= 1.6, 95%CI: 1.03-2.4) than in adult sheep (41. The infection rate in sheep with medium body condition, 57.8% (OR= 2, 95%CI: 1.3-3.1) was significantly higher (P= 0.002) than with good body condition (40.1%). The occurrence of haemonchosis in sheep was significantly varied (X2=27.73, P= 0.042) with different months of the study period. The infection rate raised from the beginning of the dry season in December (44.4%) and the highest prevalence (60.5%) was observed in January, however haemonchosis in sheep gradually decreased to the lost prevalence rate 39.2% in March. Origin of the animals was not significantly associated with prevalence of Haemonchus infection, however, p was highest in sheep brought from Bilida (56.1%) while the lowest in sheep originated from Nadda, 43.4% (OR= 0.87, 95%CI: 0.43-1.74, P= 0.68). In this study the occurrence of Haemonchus infection throughout the dry months of the study period indicates that haemonchosis is considerably prevalent disease in the study area. Hence regular and strategic deworming of sheep together with improvement of nutritional status of animals especially during the dry season in the study area are recommended.