Plant extracts play an essential role in bioreducing metal ions and capping the resultant nanomaterials. We report the green synthesis of indole pyrazole-capped cadmium sulfide quantum dots (TRPIDC-CH₃CdSQDs) using Moringa oleifera leaf extract and indole pyrazole ligand. Morphological analysis using a high-resolution electron microscope indicated the presence of spherical particles with an average diameter of 4.5 nm. The ultraviolet–visible (UV–Vis) spectroscopy results exhibited a bandgap energy of 2.95 eV, and phytochemical deposition on the TRPIDC-CH₃CdSQDs was confirmed by Fourier transform infrared (FTIR). The cytotoxicity analysis was conducted using the 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay on two cancer ((breast (MCF-7) and lung (A549)) cells and a normal human embryonic kidney (HEK293) cell. Low cytotoxic activity was found for TRPIDC-CH₃CdSQDs against all three cell types, the highest activity percentage being 63.80% against MCF-7 and TRPIDC-CH₃CdSQDs show a dose-dependent increase in cytotoxic activity. Spectroscopic interaction studies were undertaken with human serum albumin using UV–Vis and fluorescence spectroscopy. The interactions between TRPIDC-CH₃CdSQDs and human serum albumin were hydrophobic. Using corrected fluorescence data, the Stern–Volmer constant and binding constant were 2.06 × 10³ and 2.85 × 10³ mol·L⁻¹, respectively. The findings indicate its potential to be used in drug delivery.