A synergetic effect of molecular weight (Mn) and fluorine (F) on the performance of all‐polymer solar cells (all‐PSCs) is comprehensively investigated by tuning the Mn of the acceptor polymer poly((N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl)‐alt‐5,5′‐(2,2′‐bithiophene)) (P(NDI2OD‐T2)) and the F content of donor polymer poly(2,3‐bis‐(3‐octyloxyphenyl)quinoxaline‐5,8‐dyl‐alt‐thiophene‐2,5‐diyl). Both Mn and F variations strongly influence the charge transport properties and morphology of the blend films, which have a significant impact on the photovoltaic performance of all‐PSCs. In particular, the effectiveness of high Mn in increasing power conversion efficiency (PCE) can be greatly improved by the devices based on optimum F content, reaching a PCE of 7.31% from the best all‐PSC combination. These findings enable us to further understand the working principles of all‐PSCs with a view on achieving even higher power conversion efficiency in the future.