The Nanpu sag is located in the eastern part of the North China Craton and is a hydrocarbon-rich sag in the northern part of the Bohai Bay Basin. There has been a long-standing debate regarding the tectonic evolution model of the Nanpu sag, specifically whether it is formed by extensional faulting superimposed by strike-slip faulting to create a sag or if it is the result of multi-stage extensional faulting forming the sag. This study conducted structural interpretation on eight seismic profiles traversing the Nanpu sag and identified NE–SW-striking fault zones characterized by listric normal faults, domino-style normal faults, X-type normal faults, graben-horst structures, and extensional duplex structures, representing typical extensional deformation systems. The NW–SE-striking fault zones exhibited left-lateral strike-slip and oblique extension features, mainly serving to accommodate southward movement of the hanging wall of NE–SW-striking normal faults. Analysis of structural maps of stratigraphic boundaries during different geological periods in the Nanpu sag revealed a migratory pattern of the sedimentary center in the Cenozoic from NW to SE. Based on the above analysis and incorporating regional tectonic evolution data, this study proposed a four-stage tectonic evolution model for the Cenozoic in the Nanpu sag, suggesting it underwent a multi-stage extensional faulting. This work not only serves the purpose of aiding future oil and gas exploration in the Nanpu sag but also contributes valuable material for theoretical studies on fault systems.