Feed scarcity is a major challenge in smallholder production systems especially during the dry season. Sweet potato vines (SPV) contribute over 40% of the crop residues fed to dairy cattle but they are highly perishable resulting into losses of about 24% per season. Ensiling SPV mitigates seasonal feed shortages and assists in coping with seasonal feed price fluctuations. This study was conducted to evaluate the effect of sweet potato vines silage (SPVS) supplementation on the performance of lactating Ankole × Friesian crossbred dairy cattle. Four primiparous cows in early lactation were randomly allotted a basal diet of Rhodes grass (Chloris gayana) hay supplemented with dairy pellets and four graded levels of SPVS (0, 100, 200 and 300 g/kg of the daily ration) in a 4 × 4 Latin square design. The animals were given a one-week adaptation period followed by a two weeks data collection period for each diet. Dry matter intake (DMI), live weight changes, milk yield and composition were determined. Dry matter intake improved with addition of SPVS (P ≤ 0.05), with intake being highest (11.9 kg) in cows that were fed the highest SPVS level and lowest in cows that were not given SPVS (6.8 kg). Although animals on diets with 0, 100, 200 g of SPVS/kg of daily ration lost weight, there were no significant differences (P ≥ 0.05) in body weight changes across all treatments. Milk yield increased with SPVS supplementation by 1.5-1.7 kg per cow per day but there were no significant differences between the different SPVS supplementation levels. Milk fat and solids-non-fat differed (P ≤ 0.05) across the four diets but there was no consistent trend observed. Considering profit margins, supplementing dairy cows with SPVS at a level of 100 g/kg of daily ration was the most profitable at Uganda shillings 1290 (0.