Mid-upper arm circumference (MUAC) is simple to use and inexpensive in Ethiopia; both MUAC and target weight are employed, although the time to cure for MUAC is not indicated. The present study is aimed to determine cure time of MUAC for children in outpatient therapeutic program. A prospective cohort study was conducted among 414 severe acute malnourished under-five children admitted to selected health twenty-two posts from 1 February to 30 July 2021, in Oromia, Ethiopia. Data were coded, entered to Ep-data version 4.2 software, and transferred to SPSS for windows version 25 software for analysis. The Multivariate Cox Proportional Hazards model was used to fit independent determinants of time to cure. All tests were two-sided and statistical implications at P-values < 0⋅05. In the present study, the minimum week for a cure was 4 weeks, the maximum was 16 weeks and the overall time to cure severe acute malnutrition as measured by MUAC is judged to be 10 at 95 % CI (9⋅65–10⋅35). Families with six or more members are 2⋅16 times more at risk, children from homes with the lowest wealth index are at 1⋅4 times more risk, and children from food insecure families were 2⋅61 times more likely to require long-term treatment for MUAC. In the present study, the time to cure severe acute malnutrition by MUAC is determined as 10 weeks. Moreover, family size, low wealth index, and household food insecurity were risks to delay in cure time MUAC.