In the present work, we attempt to explore the size-dependent structural stability of bulk (0.28 µm) and nano-sized (25 nm) anatase TiO₂ particles under acoustic shocked conditions. Based on the observed X-ray diffractometric, Raman spectroscopic and transmission electron microscopic results with respect to the number of shock pulses, at the 90-shocked condition, the nano-size particles undergo the anatase to the rutile phase transition, whereas the bulk size TiO₂ particles remain to be in the anatase phase. From the comprehensive assessment, it is demonstrated that the bulk TiO₂ samples have higher structural stability compared to the nano-size samples. The nano-sized anatase-TiO₂ particles have values of lower thermal conductivity compared to the bulk-sized particles such that the value of lower thermal conductivity is a prominent crucial factor in initiating the dynamic recrystallization which results in the anatase-to-rutile phase transition. Based on the observed present experimental results and previous reports, it has been authenticated that, while increasing the particle size from nano-scale to micro-scale, the critical shock number for the anatase to rutile phase transition is significantly increased.