Narrow bandgap semiconductor CuBi2O4 microstructures such as three dimensional hierarchical microspheres, micro-flowers, one dimensional microrods and nanorods were fabricated through a facile hydrothermal synthesis approach by systematically changing the synthesis conditions. Their optical properties and photocatalytical performances under visible light illumination were characterized. The hierarchical micro-flower shaped CuBi2O4 sample showed a high photodecay rate of 0.114 ± 0.002 h−1 with 1 mg/ml CuBi2O4 concentration for methylene blue (30 μM). Under the illumination of an AM 1.5G solar simulator, a 0.02 mA/cm2 stable cathodic photocurrent density was observed at a low negative bias voltage (-0.25 V vs (Ag/AgCl)). The micro-flower shaped CuBi2O4 sample also showed a high antibacterial effect against Escherichia coli, with ∼ 93 % bacteria reduction after 6 h illumination by a commercial white LED light (10 mW/cm2). These results indicate that CuBi2O4 can be a promising candidate for visible light driven energy conversion and antimicrobial applications.