AbstractDeveloping efficient and stable all‐polymer solar cells (all‐PSCs) has received increasing attention because of their mechanical robustness for flexible devices. Based on the CH‐series small molecule acceptors, a new polymer acceptor (PZC24) is reported and obtains a decent power conversion efficiency (PCE) of 16.82% when blended with PM6. To further improve the performance, an oligomeric acceptor (CH‐D1), which possesses the same backbone structure as PZC24, is proposed and synthesized as the third component for all‐PSC system. The creative strategy improves the crystallinity and molecular packing, and can maintain the efficient charge transport channels of the all‐PSCs binary system. Therefore, the PM6:PZC24:CH‐D1 based ternary devices exhibit an impressive PCE of 17.40%, among the highest value of all‐PSCs. Compared to the PM6:PZC24, the ternary device exhibits enhanced photosoaking stability and thermal stability, simultaneously. In addition, the introduction of oligomeric acceptor does not weaken the mechanical robustness of all‐PSCs. As such, the ternary flexible devices display an excellent PCE of 15.35%. Importantly, this strategy shows excellent universality in PM6:PY‐IT and PM6:PY‐V‐γ all‐PSCs with improved PCEs over 17%. The results provide a feasible strategy to simultaneously improve photovoltaic efficiency and stability of all‐PSCs devices and herald a bright future for all‐PSCs.