Alternative splicing is a part of mRNA processing that expands the diversity of proteins encoded by a single gene. Studying the full range of proteins–products of translation of alternatively spliced mRNA is extremely important for understanding the interactions between receptor proteins and ligands since different receptor protein isoforms can provide variation in the activation of signaling pathways. In this study, we investigated the expression of isoforms of TNFR1 and TNFR2 receptors before and after exposure to TNFα in two cell lines that had previously demonstrated diverse effects on cell proliferation under TNFα incubation using RT-qPCR. We found that after incubation with TNFα: (1) expression of isoform 3 of theTNFRSF1Agene was increased in both cell lines; (2) the cell line with increased proliferation, K562, had decreased expression of isoforms 1 and 4 of theTNFRSF1Agene and expression of isoform 2 ofTNFRSF1Bgene was absent at all; (3) the cell line with decreased proliferation—MCF-7 had significantly increased expression of isoform 2 ofTNFRSF1Bgene. Thus, we can conclude that TNFα exposure to the K562 and MCF-7 cell lines leads to changes in the expression of TNFα receptor isoforms, which, in turn, can appear via diverse proliferative effects.