Dryland-to-paddy (D2P) conversion has been widely implemented in Northeast China and is often associated with improvements in of saline-alkali soils. However, the pathways through which climate change influences this land-use transition and subsequent saline-alkali land dynamics remain insufficiently understood. In this study, long-term climate records, land-use data, and logistic regression-based spatial analysis were used to examine the relationships among climate change, D2P conversion, and saline-alkali land dynamics in the northern Songnen Plain. Binary logistic regression models were developed to quantify the occurrence probability and spatial suitability of major land-use types, including saline-alkali land, paddy fields, and dryland, and to identify their key driving factors. The results indicate that irrigation availability, groundwater conditions, and drainage settings were the primary controls on paddy expansion, whereas climatic variables, particularly temperature, mainly defined the background feasibility. Climate warming reduced the thermal constraints on paddy expansion, but did not directly determine the spatial pattern of land-use change. Instead, irrigation and drainage conditions determined whether this feasibility was realized through D2P conversion. After 2010, land-use transitions became more directional, with D2P conversion emerging as the dominant pathway of agricultural restructuring. The reduction of saline-alkali land occurred mainly through a stepwise transition from saline-alkali land to dryland and then to paddy fields, rather than through direct conversion. In addition, D2P conversion was spatially selective and occurred primarily in areas with high paddy suitability, favorable irrigation accessibility, appropriate topographic conditions, and suitable groundwater conditions. Overall, land-use transitions in the study area reflected the combined influence of climatic background conditions and water management. D2P conversion can be interpreted as a climate-adaptive but management-dependent pathway that modifies regional water-salt conditions. These findings provide practical insights for improving irrigation and drainage management and understanding how land-use transition mediates salinity responses to climate change in saline-prone agroecosystems.