Proven RNA-based medications have elevated the demand for targeted nucleic acid-based agents. In this context, nucleic acid aptamers represent an appropriate class of molecules. They are single-stranded nucleic acid molecules that bind to a target molecule with high affinity and specificity. Aptamers have a number of advantages over antibodies including compact dimenssions, rapid tissue penetration, heat resistance, denaturation resistance, broad spectrum of targets, ease of chemical synthesis, ease of chemical alteration, convenient storage, minimal immunogenic response, negligible variability across batches, and cost-effective production. Here, we discuss whether we can use aptamers to target intracellular antigens and how they could be applied for delivering therapeutics or diagnostic agents to tumor or viral-infected cells. Here, we discuss whether we can use aptamers to target intracellular antigens and how they could be applied for delivering therapeutics or diagnostics to tumor or viral-infected cells.