This day, there is a developing trend towards working collaboratively with more and morerndonors requesting agencies to form consortia. In the literature, there are mixed opinions onrnthe effectiveness of working with consortiums. This research work investigated therneffectiveness of development project consortiums by employing a multiple case study design.rnQuantitative data was collected from 41 respondents from three selected project consortiumsrnimplemented between 2011-2017 in Ethiopia. Data has been processed using SPSS versionrn20. The study found out that these project consortiums were effective measured by tenrnsuccess factors adapted from the ECB consortium country experience and CRS CAFÉ standard.rnAssessment of the effectiveness of separate project consortiums revealed that AGP-LMDrnproject consortium was less effective than GRAD and ASPIRE project consortiums. Out of thernseven project success indicators considered in the study, a great majority of the respondentsrnassured that the consortiums effectiveness has had high contribution to the achievement ofrnfive project success indicators. However, the study finding shows mixed result on contributionrnfor two success factors. The implication of the study findings is that, if well-managedrnconsortiums are a very good project implementation model to address the most criticalrndevelopment challenges, bringing together complementary expertise of differentrnorganizations and synergy.