Polyoxometalates (POMs) are versatile anionic clusters which have attracted a lot of attention in biomedical investigations. To counteract the increasing resistance effect of cancer cells and the high toxicity of chemotherapeutic treatments, POM-based metallodrugs can be strategically synthesized by adjusting the stereochemical and physicochemical features of POMs. In the present report a polyoxomolybdate (POMo) based organic–inorganic hybrid solid (C6H16N)(C6H15N)2[Mo8O26]·3H2O, solid 1, has been synthesized and its antitumoral activities have been investigated against three cancer cell lines namely, A549 (Lung cancer), HepG2 (Liver cancer), and MCF-7 (Breast cancer) with IC50 values 56.2 μmol L−1, 57.3 μmol L−1, and 55.2 μmol L−1 respectively. The structural characterization revealed that solid 1 consists of an octa molybdate-type cluster connected by three triethylamine molecules via hydrogen bonding interactions. The electron microscopy analysis suggests the nanocapsule-like morphology of solid 1 in the size range of 50–70 nm. The UV-vis absorption spectra were used to assess the binding ability of synthesized POM-based solid 1 to calf thymus DNA (ctDNA), which further explained the binding interaction between POMo and ctDNA and the binding constant was calculated to be 2.246 × 103 giving evidence of groove binding.