For the first time, porous peanut-like Bi₂O₃–BiVO₄ composites with heterojunctions have been synthesized by a one-step mixed solvothermal method with the assistance of a L-lysine template. A mixture of ethylene glycol (EG) and H₂O (volume ratio of EG–H₂O = 3:1) is used as the solvent. Unlike the traditional methods, no concentrated HNO₃ and/or NaOH are involved in diluting Bi and V sources in the adopted approach. The as-synthesized peanut-like samples are rough and porous on the surface and to some extent are interior-hollow. The degradation of methylene blue (MB) is employed to evaluate the photocatalytic activity of the Bi₂O₃–BiVO₄ composite. It is observed that the composite performs much better than Bi₂O₃ and BiVO₄, plausibly due to heterojunctions formed between Bi₂O₃ and BiVO₄. To investigate the relationship between structure and performance, the as-synthesized samples are characterized by XRD, XPS, SEM, TEM (HRTEM), UV-vis DRS, PL and nitrogen adsorption–desorption methods. Additionally, a possible growth mechanism of this hollow peanut-like structure and the separation process of photogenerated electron–hole pairs on the heterojunctions have been discussed.