Aims:  To observe the antiobesity activity of trans‐10,cis‐12‐conjugated linoleic acid (CLA)‐producing lactobacillus in mice. Methods and Results:  Lactobacillus plantarum PL62, which can grow in the presence of linoleic acid, was selected and studied. The culture supernatant of Lact. plantarum PL62 contained trans‐10,cis‐12‐conjugated linoleic acid (6·4 μg ml−1), and the crude enzyme prepared from washed cells produced trans‐10,cis‐12 CLA (1395 μg mg−1 protein). Lact. plantarum PL62 reduced the weights of epididymal, inguinal, mesenteric, and perirenal white adipose tissues and significantly reduced the blood levels of total glucose and body weights of mice (P < 0·01). Conclusions:  trans‐10,cis‐12‐CLA‐producing Lact. plantarum PL62 can exert the same antiobesity activity as trans‐10,cis‐12‐CLA in mice. Significance and impact of the study:  trans‐10,cis‐12‐CLA‐producing Lactobacillus can be a replacement for CLA for obesity treatment via the continuous production of trans‐10,cis‐12‐CLA. The results provide a novel opportunity to develop foods with antiobesity activity.