A pot experiment was conducted in a tropical mid-elevation environment (861 m altitude) to evaluate sweetpotato (Ipomoea batatas (L.) Lam.) clones of different origin and breeding intensity for traits related to growth phenomena, nitrogen-use efficiency, and transpirational water-use efficiency (WUE) as affected by different levels of N fertilization. Genotypes with small canopies were associated with a consistently positive response in their final storage root dry matter (DM) yields to increasing N supply, and with efficient allocation of DM and N to storage roots. Genotypes with high canopy net assimilation rates (NARs) had a high proportion of leaves exposed to the sun and high chlorophyll content in leaves. Nitrogen stress led to increased transpiration per unit leaf area and decreasing WUE. Decreasing WUE under N stress was due to lower total plant DM production rather than to increased total water transpiration per plant.