Breast cancer is the fifth major cause of fatalities associated with cancer worldwide and in Pakistan, 34 066 female breast cancer cases were recorded in 2018. This study was designed to understand extracts of Cheiranthus cheiri (C. cheiri) and to evaluate the epigenetic modulation of microRNA expression for breast cancer therapy using a selected phyto-nanohybrid treatment. The phytochemical screening revealed the presence of potential phytochemicals and antioxidant scavenging activity in the C. cheiri extracts with a DPPH (2-diphenyl-1-picryl-hydroxyl) assay giving an IC₅₀ value of 20.63 μg mL^-1. GC-MS (gas chromatography-mass spectroscopy) analysis of the C. cheiri n-hexane extract detected 42 phytocompounds. Titanium oxide (TiO₂) nanoparticles were synthesized and characterized using XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDX (energy dispersive X-ray spectrometry) to confirm the synthesis of anatase (tetragonal) TiO₂. The prepared nanoparticles were conjugated with the selected plant i.e., C. cheiri. The resulting phyto-nanohybrid was used for the subsequent treatment of breast cancer induced in a female rat model. The treatment groups were as follows: doxorubicin as the standard treatment, C. cheiri, TiO₂ and the phyto-nano hybrid treatment. After 8 weeks of treatment, the groups induced to exhibit breast cancer (with and without treatment) and the control groups were dissected and analysed for histopathological, haematological and microRNA expression. Histopathological examination revealed chronic inflammation in the dilated ducts and tumour embolus formation, thus confirming the presence of breast cancer in the DMBA-induced female rat model. MicroRNA expression analysis showed a statistically significant decrease in levels of miR-205 in the plasma of the breast cancer rat model compared to the control (p < 0.05). After treatment with the phyto-nano hybrid, a statistically significant increase in the expression of miR-205 was observed in the rat models induced to exhibit breast cancer compared to the rat model without any treatment (p < 0.05). The downregulation of miR-205 in the plasma of the breast cancer exhibiting model, as compared to the control, and its upregulation after treatment with the selected phyto-nano hybrid indicated its diagnostic and prognostic significance. It is concluded that the phyto-nano hybrid used in this study is effective against breast cancer induced female rat model. All the results support the finding that the selected phyto-nano hybrid has great potential as a possible therapeutic agent for the treatment of breast cancer.