Antimonene, a novel group 15 two-dimensional material, is functionalized with an oligonucleotide as a first step to DNA sensor development. The functionalization process leads to a few-layer antimonene modified with DNA that after deposition on gold screen-printed electrodes gives a simple and efficient DNA electrochemical sensing platform. We provide theoretical and experimental data of the DNA–antimonene interaction, confirming that oligonucleotides interact noncovalently but strongly with antimonene. The potential utility of this antimonene-based sensing device is assessed using, as a case of study, a sequence from the BRCA1 gene as the target DNA. The selectivity of the device allows not only recognition of a specific DNA sequence but also detection of a mutation in this gene associated with breast cancer, directly in clinical samples.