To address ongoing food insecurity and acute malnutrition in Somalia, a broad range of assistance modalities are used, including in-kind food, food vouchers, and cash transfers. Evidence of the impact of cash and voucher assistance (CVA) on prevention of acute malnutrition is limited in humanitarian and development settings. This study examined the impact of CVA on prevention of child acute malnutrition in 2017/2018 in the context of the Somalia food crisis. Changes in diet and acute malnutrition were measured over a 4-month period among children age 6–59 months from households receiving household transfers of approximately US$450 delivered either as food vouchers or a mix of in-kind food, vouchers, and cash. Baseline to endline change in children's dietary diversity, meal frequency, minimum acceptable diet (MAD), mid-upper arm circumference (MUAC), and acute malnutrition (MUAC < 12.5 cm) were compared using difference-in-difference analysis with inverse probability weighting. There were no statistically significant changes in dietary diversity, meal frequency, or the proportion of children with MAD for either intervention group. Adjusted change in mean MUAC showed increases of 0.5 cm (confidence interval [CI; 0.0, 0.7 cm]) in the food voucher group and 0.1 cm (CI [−0.1, 0.4]) in the mixed transfer group. In adjusted analysis, prevalence of acute malnutrition among children under 5 years increased by 0.7% (CI [−13.4, 14.4%]) among food voucher recipients and decreased by 4.8% (CI [−9.9, 8.1%]) in mixed transfer recipients. The change over time in both mean MUAC and acute malnutrition prevalence was similar for both interventions, suggesting that cash and vouchers had similar effects on child nutrition status.