Candle soot carbon nanoparticles (CSC-np) collected from candle burning can be converted into an effective universal anode for metal-ion (M-ion; M = Li, Na and K) batteries. As-collected CSC-np particles exhibiting fractal-like interconnected porous carbon nanostructure chains are annealed in air (at 350 °C) and Ar (at 750 °C). The effect of annealing conditions on the structural and electrochemical performance of CSC-np are evaluated. Electrochemical studies show that a two-step annealing process yield most efficient anode and possess superior electrochemical performance for all three Li-, Na- and K-ion batteries compared to CSC-np either annealed only in air or in Ar. As-collected CSC-np, though electrochemically active, exhibit poor characteristics emphasizing the importance of annealing conditions required to activate it to be used as an appropriate anode for M-ion battery application. Detailed structural, microstructural and chemical analyses were made on CSC-np. These studies suggest that crystallinity, surface area and chemical composition of two-step annealing of CSC-np are found to be most favourable for high capacity M-ion storage. At low charging rate, capacity (current-rate) of 1247 mAh g−1 (0.15 A g−1), 461 mAh g−1 (0.02 A g−1) and 406 mAh g−1 (0.02 A g−1) and at high charging rate, capacity of 237 mAh g−1 (25 A g−1), 124 mAh g−1 (25 A g−1) and 22 mAh g−1 (15 A g−1) are realized in Li-, Na- and K-ion batteries, respectively. © 2020 Elsevier B.V.