Nanoparticles of silver were synthesised utilising water leaf extract of Elsholtzia communis (Collett and Hemsl.) Diels (ECO). The formation of Elsholtzia communis silver nanoparticles (ECO-AgNPs) was monitored by a UV-visible spectrophotometer. From the TEM and XRD analysis, the average particle and crystallite size of ECO-AgNPs was determined as 11.38 nm and 8.52 nm, respectively. DLS studies of ECO-AgNPs showed the ζ-potential value of −59.4 mV and a polydispersity index (PDI) of 0.149. The phytochemicals responsible for the reduction of silver ions were confirmed through FTIR spectroscopy and further supported by HRLC-MS analysis. Dose-dependent antioxidant and antidiabetic activities were demonstrated by the biosynthesized nanoparticles. The antiproliferative activity of ECO-AgNPs was estimated using 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay on HeLa, HCT 116 and A549 cell lines and their IC50 values were found to be 71.33 ± 2.89 µg/mL, 33.45 ± 0.21 µg/mL, and 28.91 ± 5.01 µg/mL, respectively. The results showed that Elsholtzia communis AgNPs have enhanced antiproliferative, antioxidant, and antidiabetic activities and may be employed as beneficial nanocompounds.