The use of organic semiconductors in bioelectronic devices has received considerable attention over the past decade, since they have the potential to form an excellent biointerface for living cells and tissues. The aim was to determine multiple aspects of the biocompatibility of selected organic semiconductors with high conductivity and to further improve their potential for cell cultivation. Two representatives of low-molecular weight organic semiconductors triisopropylsilyethynyl pentacene (TIPS-Pentacene) and diketopyrrolopyrrole (DPP(TBFu)2) were selected together with two semiconducting organic polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The stability of these materials in physiological environment and their wetting properties, which are preconditions for biocompatibility, were determined. TIPS-Pentacene, DPP(TBFu)2 and P3HT were stable but PEDOT:PPS produced some leachates. Native TIPS-Pentacene, DPP(TBFu)2 and P3HT exhibited lowered wettability. Their biocompatibility was studied by means of fibroblasts and differentiated cardiomyocytes. It was limited compared to standard cell culture plastics, thus coating of surface by proteins was applied. Among others collagen IV coating was shown to significantly improve biocompatibility of all tested organic semiconductors. Finally, cultures of spontaneously beating cardiomyocytes were established on TIPS-Pentacene, DPP(TBFu)2, P3HT and PEDOT:PSS.