ABSTRACT Sweet potato is a vegetable with great potential due to its versatility of use, which covers human food, animal feed and biofuels. However, it is still little studied, especially regarding mineral nutrition and potassium. Thus, a study was conducted to evaluate potassium fertilizer doses (0, 30, 60, 90, 120 and 150 kg/ha K2O) on mineral nutrition and yield of 'Beauregard' sweet potato in a typic Hapludult soil with low K level (0.3 mmolc/dm3). The experimental design was of randomized blocks with four repetitions. Harvest took place 123 days after seedling transplanting. Foliar K content, shoot, root and total dry matter, root total yield, root commercial yield, K accumulation, K content in the soil and K optimal economic dose were assessed. The highest foliar K content was observed at the dose of 100 kg/ha K2O, with K value of 44.6 g/kg on leaf dry matter. In soils with low K availability, the highest yield (38 t/ha) was observed at the dose of 87 kg/ha K2O. Maximum commercial yield (24.3 t/ha) was obtained at the dose of 85 kg/ha K2O, and K accumulation of 150 kg/ha in the shoot and 57 kg/ha in the root, respectively, were observed (72.5 and 27.5%). Optimal economic production was of 71 kg/ha K2O, which corresponds to 83% of the dose that maximized commercial production.