•This work reviews advances of bio-carbon KIBs anode with diverse microstructures.•A discussion on biomass carbons and biomass carbon-metal composites are presented.•The geometries, synthesis, and electrochemical characteristics are both summarized.•Investigations on the electrochemical kinetics of bio-carbon KIBs anode are provided.•Perspectives to achieve structurally-tuned bio-carbon KIBs anode are highlighted. Pursuit of advanced batteries with high energy density and low cost is the eternal goal for electrochemists. Potassium-ion batteries (KIBs) become a core focus to meet the need for scalable power sources in both academic and industrial energy-harvesting area. As the key to boosting development of KIBs, the advancement of high-performance anode materials helps to increase their competitiveness and feasibility. In this sense, biomass-based carbon materials with elaborate biological structures, strong physicochemical adsorptions, environmental benignity and cost effectiveness tick almost all the right boxes as a material for biocompatible energy-storage systems. More importantly, their intrinsic diversity of bio-microstructures provide considerable merits involving rapid ion/electron channels, strengthened mechanical substrates as well as in-situ templates for further electrode designs, allowing for achieving structurally-tuned surface chemistry in KIBs anodes. In this review, by focusing on the aspects of pure biomass carbons and biomass carbon-metal composites, a rapid glimpse at biomass carbon-based anode materials with various micro-architectures is provided, covering the architectural geometries, synthetic strategies, energy-storing mechanisms and electrochemical characteristics. In addition, a brief perspective on the imminent challenges and future directions of bio-carbon anodes in KIBs is also highlighted. We hope to cast a valuable outlook for structurally-controlled biomass-based anode materials in KIBs.