The aim of the study conducted in 2019–2021 was to determine the effect of biostimulants and growth regulators on the yield size and structure, as well as the chemical composition of edible potato tubers. The cultivar evaluated was Vineta. Asahi SL, Kelpak SL, Aminoplant, Tytanit, gibberellic acid (GA3) and Moddus 250 EC were applied in potato cultivation. The application of biostimulants Asahi SL and Tytanit increased the total and marketable tuber yield, as well as the average tuber weight. Aminoplant had a beneficial effect only on the marketable yield, while Moddus 250 EC decreased tuber yield and mean tuber weight, especially under conditions of high rainfall. Biostimulant Asahi SL caused a decrease in the number of tubers formed, while gibberellic acid stimulated tuberisation. Both preparations increased the share of deformed tubers in the total yield. The effect of biostimulants and growth regulators on the formation of the chemical composition of potato tubers was multidirectional. Tytanit increased protein content in tubers, while the remaining preparations, with the exception of the growth regulator Moddus 250 EC, decreased the amount of this component. GA3 and Moddus 250 EC decreased the content of crude fibre and, in the case of Moddus 250 EC, also the content of mineral components. The highest concentration of nitrates (V) was characteristic for potato tubers treated with Asahi SL and the lowest for those treated with Moddus 250 EC.