Background: About 24 million children across the world live without their parents. In resource-limited countries like Ethiopia, childhood malnutrition is common and intertwined with poverty. It is a leading cause of death for children contributing over half of child mortality in sub-Saharan Africa. Nevertheless; little is known about the prevalence of malnutrition and associated factors among under five age orphans, as most of the variable studies were geared towards under five children as wholesome. Method: A community based cross-sectional study design complemented with qualitative methods was conducted collecting data from mothers/caretakers of 367 orphans in Dilla town, Southern Ethiopia from 5, Dec.2017-18, Jan. 2018. Systematic random sampling technique was used, A structured pretested interviewer administered questionnaire complemented by focus group discussions and key informant in-depth interviews" was used. Anthropometric measurements were also carried. Data were entered in to EPi-info version 3.5.4 software and exported to SPSS version 20 for analysis. The prevalence of wasting among Orphans was assessed by calculating the percentages using ENA for SMART 2012 software and analysis was made using WHO Standard cut off point below-2 S. D using z-scores. All variables with p value of < 0.25 during bivariate logistic regression analysis were entered to a multivariate analysis to identify variables independently associated with the outcome variable at p value 0.05 with 95% CI. For qualitative aspect, thematic framework analysis was employed. Results: 11.1% orphans were wasted from which 3.3 are severely wasted. The main associated factors of wasting were found to be number of under-five orphans at home (AOR 1.420; 95% CI 1.094-3.086), duration of breast feeding (AOR 2.039; 95% CI 1.027-4.048), marital status of care givers (AOR 1.482; 95% CI 1.692-3.377), age when complementary meal started (AOR 2.023; 95% CI 1.028-3.980), wealth index (AOR 2.558; 95% CI 1.074-3.515) and access to balanced diet (AOR 2.022; 95% CI 1.026-3.889) Conclusion: The prevalence of wasting is high among under-five orphans; therefore, all concerned bodies should pay a great attention for proposed interventions like Strengthen the social interactions and indigenous institutions to maximize social care for under five orphans and Integrating locally available nutrition support programs to reach under 5 yrs orphans.