Introduction The biosynthesis of metal nanoparticles using medicinal plants is not only economical but also environmentally friendly as well as having miscellaneous biomedical applications. In the present study, silver nanoparticles were green-synthesized using the aqueous extract of Calendula officinalis. Material and methods The synthesized AgNPs@Calendula officinalis were characterized by analytical techniques including EDX, FE-SEM, XRD, UV-Vis., and FT-IR. The anti-human colorectal cancer activities of AgNPs@Calendula officinalis were evaluated using MTT assay. Results The nanoparticles were formed in a spherical shape in the range of 38.05 to 75.41 nm for the particle size. On the other hand, the MTT assay was run to evaluate anti colorectal cancer activity of AgNPs@Calendula officinalis. In the cellular and molecular part of the recent study, the treated cells with AgNPs@Calendula officinalis were assessed by MTT assay for 48 h about the cytotoxicity and anti-human colorectal carcinoma properties on normal (HUVEC) and colorectal carcinoma cell lines i.e. WiDr, SW1417 [SW-1417], and DLD-1. In the antioxidant test, the IC50 of AgNPs@Calendula officinalis and BHT against DPPH free radicals were 222 and 124 µg/mL, respectively. The viability of malignant colorectal cell line reduced dose-dependently in the presence of AgNPs@Calendula officinalis. The IC50 of AgNPs@Calendula officinalis were 430, 326, and 392 µg/mL against WiDr, SW1417 [SW-1417], and DLD-1 cell lines, respectively. Conclusions After the clinical study, silver nanoparticles containing Calendula officinalis leaf aqueous extract may be used to formulate a new chemotherapeutic drug or supplement to treat the several types of human colorectal carcinoma.