The origins of overpressure in the central Xihu depression have been accepted to result from disequilibrium compaction and hydrocarbon generation. This study uses organic matter correction of the log data in source rocks and five empirical methods (the multilogging combination method, Bowers’ method, the sonic velocity–density crossplot method, the porosity method, and the pressure inversion method) to understand the origins of overpressure in the central Xihu depression. Overpressure strata are mainly distributed in the following two areas: the (1) Pinghu Formation on the western slope of the central Xihu depression and (2) Pinghu Formation and lower part of the Huagang Formation in the western sag and the central inversion anticline belt. The areas contain two types of pressure profiles: normal pressure–overpressure and normal pressure–overpressure–normal pressure. At the western slope and the western sag, overpressure in source rock and nonsource rock was caused by hydrocarbon generation and pressure transfer, respectively. At the central inversion anticline belt, however, overpressure was caused by hydrocarbon generation and tectonic compression in source rock and by pressure transfer and tectonic compression in nonsource rock. We also propose criteria for confirming the combination of tectonic compression and hydrocarbon generation as the origin of overpressure, where the porosity distribution in the overpressured mudstone is consistent with the normal compaction trend or conforms to a higher level of normal compaction as the depth increases. In the sonic velocity–effective stress diagram, sonic velocity increases with decreasing effective stress, whereas density and sonic velocity both increase with increasing normal compaction in the density–sonic velocity diagram.