Achillea fragrantissima
(
A. fragrantissima
), a desert plant, is used internally in Arabian traditional medicine to treat inflammatory, spasmodic gastrointestinal disorders, and hepatobiliary diseases. The study focuses on the environmentally friendly production of silver nanoparticles (AgNPs) from the water-based aerial parts of the
A. fragrantissima
plant and their ability to kill bacteria and cells. Ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) were used to describe the AgNPs. They were then tested for their ability to fight cancer and bacteria. A change in colour from yellow to brown and a surface plasmon resonance peak at 440 nm, seen with UV-Vis spectroscopy, showed that AgNPs had formed. In a Gas Chromatography-Mass Spectrometry (GC-MS) test of the aerial parts of
A. fragrantissima
, twenty bioactive components were found. These included isolongifolol and 3E,10Z-Oxacyclotrideca-3,10-diene-2,7-dione, methylbuta-1,3-dienyl)-7-oxabicyclo [4.1.0] heptan-3-ol. The extract exhibited high phenolic and flavonoid content (77.52 ± 1.46 mg GAE/g dry weight and 59 ± 2.17 mg QE/g dry weight, respectively). According to the IC
50
values of 17.2 ± 1.18 and 14 ± 2.43 µg/mL, the AgNPs had a lot of power to kill cancer cells from the MCF-7 and HepG2 lines. Some genes that cause cell death (
caspase-3
,
8
,
9
, and
Bax
) were turned on more in the treated cells compared to the control cells that had not been treated. These genes were
Bcl-xL
and
Bcl-2
. Additionally, substantial activity against both Gram-positive bacteria and Gram-negative bacteria was found by antibacterial screening. Overall, this study underscores
A. fragrantissima’s
diverse biological activity and its potential in drug discovery and nanomedicine, promoting the development of natural antibacterial and anticancer therapies.