Objectives Ethiopia has been hesitant to shift to the global MUAC-based definitions for acute malnutrition given the two to four times potential increase in caseload suggested by several cross-sectional surveys. Thus, the objective of this study was to provide specific evidence on the caseload implications for Ethiopia of aligning with the WHO recommended criteria. Methods A cluster-randomized control study was conducted in four districts of Amhara and Oromia regions of Ethiopia in a total of 36 health posts (HPs). Districts and HPs were selected based on previous high case report. In each district, an equal numbers of HPs were randomly assigned to use either the global MUAC criteria of <11.5 cm for severe acute malnutrition (SAM) and the moderate acute malnutrition (MAM) criteria of ≥11.5cm to <12.5 cm (intervention) or the current Ethiopian criteria of <11 cm for SAM and ≥11 cm to <12 cm for MAM (control). All 6–59 mo children were screened regularly for 16 wks. Malnourished children were admitted to the study according to the criteria assigned to their HP. Results A total of 349 SAM and 986 MAM new cases were admitted during the 16 wk recruitment. Of the new SAM cases, 225 were in intervention and 124 were in control HPs. The ratio of SAM in intervention compared to control HPs was 1.78 (1.14–2.42, 95%CI), which indicates an increase in admissions of 78% (P = 0.019). The mean (±SD) monthly SAM admissions per HPs were 1.71 (0.53) in control and 2.97 (3.31) in intervention (P = 0.191). For MAM, 592 cases were in intervention and 394 were in control for a ratio of 1.50 (1.11–1.89). The global MUAC criteria increased caseload by 50% (P = 0.015) compared to control. The mean monthly new MAM admissions per HPs were 5.47 (4.02) in control and 8.22 (3.28) in intervention (P = 0.045). The mean number of children served during biweekly combined sessions for SAM and MAM was 19.67 (9.28) in intervention and 13.08 (8.28) in control (P = 0.026). For sessions restricted to SAM, a mean of 4.26 (4.11) was served in intervention and 1.92 (1.88) in control (P = 0.028). Conclusions The increases in cases and workload resulting from shifting from Ethiopia's current national SAM and MAM admission and discharge criteria to the WHO criteria are likely to be on a smaller scale than is usually claimed based on various cross-sectional surveys. Most HPs were not overwhelmed due to the shift. Funding Sources Bill and Melinda Gates Foundation.