Use of Mycobacterium brumae for the treatment of bladder cancer. The present invention relates to the treatment of bladder cancer, preferably superficial, non-invasive bladder cancer by using mycobacteria Mycobacterium brumae. Therapy described in this invention is particularly effective in grade 1 (well differentiated) and grade 2 (moderately differentiated) tumor cells. This makes it possible to treat the disease, which is still in an early stage, by reducing the risk of disease progression to a more harmful stage and/or preventing the risk of metastasis.