Polydopamine (PDA), which is biodegradable and is derived from naturally occurring products, can be employed as an electrode material, wherein controllable partial oxidization plays a key role in balancing the proportion of redox‐active carbonyl groups and the structural stability and conductivity. Unexpectedly, the optimized PDA derivative endows lithium‐ion batteries (LIBs) or sodium‐ion batteries (SIBs) with superior electrochemical performances, including high capacities (1818 mAh g−1 for LIBs and 500 mAh g−1 for SIBs) and good stable cyclabilities (93 % capacity retention after 580 cycles for LIBs; 100 % capacity retention after 1024 cycles for SIBs), which are much better than those of their counterparts with conventional binders. Mussel power: A polydopamine‐derived material can act as both electrode and binder material for lithium‐ion and sodium‐ion batteries, and exhibits superior electrochemical performances including high capacity and stable cyclability. The material is synthesized by the oxidative polymerization of dopamine, which is both naturally occurring and biodegradable.