Aptamers are single-stranded RNA or DNA oligonucleotides that are three-dimensionally structured and bind to a target molecule with high specificity and affinity selected from oligonucleotide libraries by systematic evolution of ligands by exponential enrichment (SELEX). This makes them stand as exceptional candidates for use as diagnostic tools or as antagonists or agonists of therapeutic targets, among others. Histone Acetyltransferase 1 (HAT1) belongs to the HATs family of enzymes. In fact, it was the first to be described within this group, although it is the least known. However, in recent years it has aroused growing interest due to its involvement in multiple pathologies. The Overexpression of this enzyme is related to a poor prognosis and survival in cancer patients as well as viral infections and other pathologies in which inflammation occurs. Thus, many authors propose HAT1 as a potential therapeutic target. In this work, aptamers were developed against this target in order to inhibit its activity. After 6 rounds of selection, 2 specific aptamers against HAT1 were obtained and were subsequently characterized and optimized. Finally, an in vitro HAT1 activity assay was performed, showing that both aptamers and their modified sequences were able to inhibit the activity of this enzyme at concentrations in the nanomolar range.