AgNP and Au@Ag treatments modulate the tumour-promoting activity of cancer-associated fibroblasts. To analyse whether nanoparticle treatments can affect the tumour-promoting activity of CAFs, first, a co-culture system was established in which 4T1 or MCF-7 tumour cells were grown in the lower chambers and NIH/3T3 or primary CAF cells were cultured separately in the upper compartments of 0.4 μm pore-sized transwell inserts (a). Wound healing activity of 4T1 or MCF-7 cells was monitored after selective treatment of NIH/3T3 or CAF fibroblast cells with non-toxic concentrations of metal nanoparticles. Experiments revealed that AgNPs and Au@Ag nanoparticles disrupted the fibroblast-induced, elevated wound healing activity of both 4T1 (b) and MCF-7 (c) cells. Similar experiments were performed using the conditioned media of AgNP, AuNP or Au@Ag nanoparticle-pre-treated NIH/3T3 and primary CAF cells. When adenocarcinoma cells were treated with the fibroblast-conditioned media, cell-free zones were scratched to the confluent cancer cell layers, then the area of the cell free zones were measured 24 h later to calculate wound healing activity. AgNP and Au@Ag treatments decreased the wound healing-promoting activity of both NIH/3T3 (d) and primary CAF cells (e). *P ≤ 0.05; ***P ≤ 0.001; ****P ≤ 0.0001 indicates statistical significance (unpaired t-test).