Herein, Ho³⁺/Yb³⁺ co-doped Si₃N₄ branched nanowires (Si₃N₄:Ho³⁺/Yb³⁺) were fabricated via plasma arc technique, and then characterized by means of X-ray diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Results indicate that the branched nanowires comprise a main trunk with multiple branches growing in parallel along both sides, while the Ho³⁺ and Yb³⁺ ions were successfully incorporated into the branched nanowire structure of Si₃N₄. Under 980 nm laser excitation, the Si₃N₄:Ho³⁺/Yb³⁺ branched nanowires exhibit three distinct up-conversion (UC) luminescence peaks: green emission at 540 nm corresponds to the (⁵F₄,⁵S₂→⁵I₈) transition of Ho³⁺; while the red emissions at 660 nm and 756 nm are attributed to the (⁵F₅→⁵I₈) and (⁵F₄→⁵I₇) transitions, respectively. Based on the UC emission intensity ratio and decay lifetime, the optical temperature sensing performance of the Ho³⁺/Yb³⁺ co-doped Si₃N₄ branched nanowires was systematically investigated over the temperature range of 298-558 K. It follows that the method for temperature measurement based on the I₅₄₀/I₆₆₀ intensity ratio achieves a maximum relative sensitivity of 2.13% K^-1. Meanwhile, the relative sensitivity based on the decay lifetime of the 540 nm emission peak reaches 1.10% K^-1. The above findings prospect the great potential in application of the Ho³⁺/Yb³⁺ co-doped Si₃N₄ branched nanowires for optoelectronic devices, biomedicine, high-precision temperature sensing, and laser technologies.