Ultrathin Co₃O₄ nanosheets are excellent candidate materials for high performance chemiresistive gas sensors. However, the restacking and aggregation of nanosheets during sensor fabrication greatly impact the sensing response. In this work, by adding the structure-directing agent of glucose, hierarchical flower-like Co₃O₄ nanostructures assembled by porous nanosheets were synthesized through hydrothermal method with subsequent calcination treatment to further improve the sensing performance. The fabricated hierarchical flower-like Co₃O₄ sensor exhibited the highest response of 48.1 toward 100 ppm acetone at 130 °C, which was 7.2 times higher than the Co₃O₄ microplates synthesized without glucose. The excellent long-term stability and selectivity of gas sensors were further validated and the theoretical limit of detection was experimentally calculated to be as low as 200 ppb. Flower-like Co₃O₄ nanostructures for acetone gas sensor with good performance provide a promising candidate to fabricate high performance gas sensor for safety monitoring and health care.