Doping of polymeric semiconductors limits the miscibility between polymers and dopants. Although significant efforts have been devoted to enhancing miscibility through chemical modification, the electrical conductivities of n‐doped polymeric semiconductors are usually below 10 S cm−1. We report a different approach to overcome the miscibility issue by modulating the solution‐state aggregates of conjugated polymers. We found that the solution‐state aggregates of conjugated polymers not only changed with solvent and temperature but also changed with solution aging time. Modulating the solution‐state polymer aggregates can directly influence their solid‐state microstructures and miscibility with dopants. As a result, both high doping efficiency and high charge‐carrier mobility were simultaneously obtained. The n‐doped electrical conductivity of P(PzDPP‐CT2) can be tuned up to 32.1 S cm−1. This method can also be used to improve the doping efficiency of other polymer systems (e.g. N2200) with different aggregation tendencies and behaviors. The dynamic behaviors of conjugated polymer aggregates in solution are correlated with the solid‐state doping efficiency of polymer films. The n‐type electrical conductivity of the polymer P(PzDPP‐CT2) can be significantly enhanced by controlling the dynamics of solution‐state aggregates. The method is general and can be used for other polymer systems with different aggregation tendencies and dynamic behaviors.