An experiment was conducted at Angacha Research Station in Kembata Tembaro Zone of Southern Ethiopia to evaluate the response of potato (Solanum tuberosum L.) to potassium fertilizer. Increasing rates of K (0, 40, 80, 120, 160, 200, 240, 280, and 320 kg ha-1 as KCl) in RCBD with four replications were used in the experiment. Recommended rates of N and P, 111 and 39.3 kg ha-1, respectively were applied to all treatments. Urea (46-0-0) and DAP (18-46-0) were used as sources of N and P. N was applied in split at planting and after tuber initiation (as side dressing). The composite soil sample contains moderate organic carbon (1.6%), whereas the total N (0.26%), available P and K contents are high. The potato tuber yield ranged between 43.97 t ha-1 at application of 200 kg K ha-1 and 53.33 tha-1 at application of 280 kg K ha-1. Application of K did not significantly influence potato tuber yield, N, P and K concentrations both in leaf and tuber, exchangeable and available potassium in the soil. However, a yield advantage of 11.4% (5.47 t ha-1) was obtained from the application of 280 kg K ha-1 over the control, although the difference is not statistically significant. These parameters neither showed increasing or decreasing pattern with increased K application. Based on the current finding, application of K for potato at Angacha is not required. However, as potato is highly K demanding crop, periodic checking of the K status of the soil and crop response to it is important.