Potassium (K) is essential nutrient to the physiological and biochemical activities of plants, acting in the cation-anion balance, water movement, osmoregulation, and transference of energy. This study aimed to evaluate the yield response of the zucchini squash cultivar 'Caserta' to different doses and sources of potassium. The experiment was carried out under field conditions in a complete randomized block experimental design in a 6 x 2 factorial scheme, with six K2O doses (0, 50, 100, 150, 200, and 250 kg ha-1) and two sources (chloride and potassium sulfate), with four replications. The fruit mass, fruit length, number of fruits per plant, total and marketable fruit yields were evaluated. The results showed that the sulfate and potassium chloride sources promoted the maximum length and number of fruits per plant. K2O fertilization in the form of potassium sulfate promoted higher mass and total fruit yield. The doses of 108.41 and 130.78 kg ha-1 of K2O in the chloride and potassium sulfate sources provided the maximum marketable yield of fruits, with 22.84 and 27.0 t ha-1, respectively. Regardless of the source, potassium fertilization must be provided to increase the production parameters of the zucchini squash 'Caserta' cultivar.