We herein report, for the first time, the activity of copper indium selenide/zinc sulphide core-shell quantum dots (CISe/ZnS QDs) as an inhibitor against recombinant human furin, an enzyme that has been implicated in the aetiology of many diseases, including Covid-19. The cell viability of the as-synthesised CISe/ZnS QDs was tested against mouse colon carcinoma cells (C26), while the Furin activity was measured by hydrolysis of peptide substrate Pyr-RTKR-AMC liberating the fluorogenic 7-amino-4-methyl coumarin. The result showed that the as-synthesised stable near-infrared emitting (840 nm) CISe-ZnS QDs is biocompatible against C26 and can inhibit furin with an inhibition constant, Ki, of 15.66 μM. The IC50 was 11.29 ± 0.54 μM, while the enzymatic activity was abolished at about 23 μM of the inhibitor concentration. The results indicate the chemotherapeutic potential of CISe-ZnS QDs as an enzyme inhibitor, which may find application in managing diseases whose pathogenesis involves hyperactivity of furin.