Sunflower is a critical oilseed crop that underpins global food security. As the world's largest exporter of sunflower oil, Ukraine produced 6.89 million tons in 2021, accounting for approximately one-third of global production. However, the ongoing Russia–Ukraine conflict has severely disrupted the local agricultural system, and the specific impacts on sunflower production dynamics remain unclear. To address this, we constructed a comprehensive monitoring framework by integrating Sentinel-1 Synthetic Aperture Radar (SAR) and Sentinel-2 optical imagery. First, we mapped annual sunflower cultivation distributions from 2019 to 2023 using an automated sample extraction method coupled with a Random Forest model, achieving an overall classification accuracy of 94.35%. Second, we implemented grid-based production prediction to capture fine-scale agricultural productivity heterogeneity. The results reveal a 49.5% decline in sunflower cultivation area between 2021 and 2022, accompanied by severe landscape fragmentation. Notably, the loss pattern exhibited a distinct “strip-like” distribution along the conflict frontline. Regarding production, while total output collapsed, the trend in unit yields diverged from the drastic reduction in cultivated areas, suggesting a potential shift in the agricultural production mode toward concentration. Finally, analysis based on multi-source indicators confirmed that farmland destruction, personnel loss, and water source damage were the drivers of agricultural decline in the region. These findings highlight the high vulnerability of agricultural systems under armed conflict and provide critical insights for post-conflict agricultural recovery and sustainable land use policymaking.