Sodium-ion batteries (SIBs) are emerging as promising alternatives to lithium-ion batteries owing to the abundant availability of sodium resources and the limited supply of lithium raw materials. However, the development of high-performance anode materials remains a critical challenge owing to the relatively low initial coulombic efficiencies (ICEs) and limited reversible capacities of conventional carbon-based anodes. Herein, hard carbon (HC) from mangrove wood is synthesized via controlled carbonization and its electrochemical performance is systematically investigated. HC prepared by carbonization at 1200 °C (MWHC-1200) exhibits the best performance, delivering a high reversible capacity of 266.6 mAh g−1 and an ICE of 75%. Pitch-derived soft carbon coatings (containing 5, 10, or 15 wt% pitch) are applied to HC synthesized at the optimal carbonization temperature to further enhance Na⁺ storage performance. Notably, the composite containing 10 wt% pitch (PC-10) exhibits the best electrochemical performance, delivering a high reversible capacity of 291.5 mAh g−1, an ICE of 82%, a capacity retention of 90.4% after 200 cycles, and an excellent rate capability. These improvements are attributable to suppressed irreversible reactions and enhanced interfacial stability. This study offers a simple yet effective approach for improving the electrochemical properties of biomass-derived hard carbon, and provides insight into the designs of practical SIB anodes.