Loess deposits serve as crucial archives of chemical weathering in arid to semiarid regions and provide robust materials for estimating the average chemical composition of the upper continental crust (UCC). This study investigated and compared cadmium (Cd) isotope variations in two typical loess–paleosol sequences from the Weinan (southeastern Loess Plateau, with moderately weathering) and Yuanbu (northwestern Loess Plateau, with weak weathering) sections of the Chinese Loess Plateau to elucidate the behavior of Cd isotopes during weathering and to further define the average δ114Cd value of the UCC. The Weinan profile with stronger weathering intensity presents pronounced isotopic differences between loess (–0.06 ± 0.15‰, 2SD, N = 11) and paleosols (–0.35 ± 0.23‰, 2SD, N = 5). There is no correlation between δ114Cd and either grain sizes or major and trace element concentrations, indicating that dust sources and aeolian sorting have minimal influences on the bulk Cd isotopic compositions of Weinan samples. Conversely, the larger Cd isotope variations observed in this more intensely weathered profile suggest that pedogenesis and chemical weathering are the primary processes responsible for Cd isotopic fractionation. Sequential leaching experiments on samples from the Weinan profile revealed that the carbonate fraction in loess has higher δ114Cd values than those in the paleosol, indicating that more Cd with heavy isotopes in the carbonate fraction of the paleosol was leached away during chemical weathering. On the other hand, the oxide fraction has extremely low δ114Cd values (–0.86‰ to –0.46‰), likely reflecting the preferential adsorption of light Cd isotopes onto Fe oxides. The limited δ114Cd variation of Yuanbu loess reflects that it was not strongly modified owing to the low degree of chemical weathering; thus, its mean δ114Cd value of 0.05 ± 0.09‰ (2SD, N = 9) can be regarded as the average composition of the UCC that aligns with previous estimates.