In this work, cocoa bean extract (CBE) was used to synthesize silver nanoparticles (AgNPs) under ambient conditions. The fairly polydispersed spherical CBE-AgNPs had size range of 8.96–54.22 nm with λmax occurring at 438.5 nm. The prominent peaks at 3275.13 and 1635.54 cm⁻¹ from FTIR data laid credence to the involvement of phenolics and proteins in the biofabrication and stabilization of CBE-AgNPs. Energy dispersive X-ray and selected area electron diffraction studies showed the conspicuous presence of silver in colloidal solution with distinctive crystalline face-centered cubic phase of AgNPs. CBE-AgNPs showed appreciable activities against multi-drug resistant bacteria, producing zones of inhibition of 10–14 mm, and also enhanced activities of ampicillin, cefuroxime, cefixime and erythromycin by 42.9–100 % in synergistic studies. It produced pronounced antimicrobial activities against several bacteria and fungi, when incorporated into emulsion paint. Furthermore CBE-AgNPs showed good larvicidal activities against Anopheles gambiae mosquito larvae with LC₅₀ of 44.37 µg/ml, while it also prevented the coagulation of human blood. This study established synthesis of AgNPs using CBE as a viable green route approach, with remarkable antimicrobial, larvicidal and anticoagulant activities. As far as we know, this is the first report of the use of CBE to synthesize AgNPs.