<p>When micro/nano-scale gradient coatings are subject to large thermal gradients or high heat fluxes, the spatial size effect cannot be ignored. It is important to understand how the size effect influences the thermal fracture behavior of functionally graded coating/substrate structures. This study aims at analyzing the transient thermal fracture behavior of collinear interface cracks in functionally graded coating/substrate structures based on the nonlocal dual-phase-lag heat conduction model. By means of integral transform techniques, the mixed boundary problem is transformed into a set of singular integral equations, which are solved by the Chebyshev polynomials. The effects of the nonlocal parameter, coating thickness, crack spacing, and non-homogeneous parameters on the temperature and stress intensity factors (SIFs) are examined. The numerical results show that these parameters play an essential role in controlling the thermal fracture behavior of the structures, especially at micro/nano-scales.</p>