Self-compacting concrete (SCC) used in the impermeable facing of rockfill concrete dams in cold and arid regions is often exposed to coupled low-temperature and low-humidity curing, which significantly affects its early-age performance. This study investigated the evolution of compressive response and pore structure of SCC at 3, 7, 14, and 28 d under three representative curing regimes, namely 20 C-degrees-95% RH, 10 C-degrees-75% RH, and 3 C-degrees-50% RH. Uniaxial compression tests, low-field nuclear magnetic resonance (LF NMR), scanning electron microscopy (SEM), and fractal analysis were employed to establish quantitative structure-property relationships. The results show that coupled low-temperature and low-humidity curing markedly suppress the development of compressive strength and elastic modulus. At 28 d, the compressive strength and elastic modulus under 3 C-degrees-50% RH were 13.90 MPa and 14.51 GPa, respectively, which were only 60.6% and 46.3% of those under 20 C-degrees-95% RH. Meanwhile, peak strain increased and the post-peak softening became more gradual under uniaxial compression. Microstructural analyses reveal that adverse curing conditions inhibit hydration, delay pore refinement, and maintain a higher fraction of harmful pores, with the persistence and interconnection of large pores governing mechanical deterioration. A modified Weibull-based uniaxial damage constitutive model incorporating both curing-induced initial damage and loading-induced damage was established. The model shows good agreement with the experimental uniaxial stress-strain curves under the tested curing regimes. This study provides an experimental and modeling basis for evaluating the early-age uniaxial compressive response of SCC under coupled low-temperature and low-humidity curing.