Diabetic peripheral neuropathic pain (DPNP) is a common manifestation of diabetic peripheral neuropathy (DPN). Although the pathogenesis of DPNP remains unclear, the disinhibition of spinal dorsal horn neuronal circuitry mediated by endoplasmic reticulum stress (ERS) is an important mechanism underlying neuropathic pain (NP). Tanshinone II A is mainly used to treat cardiovascular diseases but has also been shown to relieve various types of neuralgia, including DPNP. This study investigated the effects of tanshinone IIA in DPNP model rats. We divided animals into two groups: 1) the model (diabetic) group and 2) the tanshinone II A-treatment group. Our results demonstrated that diabetic rats exhibited a decrease in the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL), and that NMT is increased and TWL is prolonged in rats treated with tanshinone II A. Additionally, the levels of ERS-signaling pathway factors in the spinal dorsal horns of rats were lower in the tanshinone IIA-treated group than in the diabetic group. Overall, our study demonstrated that the disinhibition of spinal dorsal horn neuronal circuitry mediated by endoplasmic reticulum stress underlies DPNP and is modulated by tanshinone IIA treatment.