Hierarchical NaV₆O₁₅ flower-like structures were successfully synthesized via a facile hydrothermal reaction combined with subsequent thermal transformation. The as-prepared NaV₆O₁₅ microflowers are composed of many nanoneedles with a width of about 200 nm and a length of several micrometers. The electrochemical performance of NaV₆O₁₅ microflowers as cathodes for both lithium and sodium ion batteries are investigated. High first discharge capacities of 255 mA h g⁻¹ (vs. Li⁺/Li) and 130 mA h g⁻¹ (vs. Na⁺/Na) are observed and the capacity retention reaches 105% and 64% after 50 cycles under 4–1.5 V at a current density of 100 mA g⁻¹ and 50 mA g⁻¹, respectively. High lithium/sodium ion diffusion coefficients play an important role in improving the electrochemical performance of NaV₆O₁₅ microflowers.