Kalanchoe brasiliensis (Kb) is a medicinal plant from the Crassulaceae family, used in folk medicine to treat inflammatory and infectious diseases. Here we show that short-term treatment of mice with a highly purified compound named kalanchosine dimalate (KMC), obtained from Kb, led to a strong and selective inhibition of B cell development in the bone marrow, without affecting the myeloid lineage development. Numbers of mature B lymphocytes in bone marrow or peripheral lymphoid organs were preserved in KMC treated mice. The inhibitory effect of KMC was acute and rapidly reverted with the interruption of the treatment. In vitro, KMC, inhibited the interleukin-7 dependent proliferation of B cell precursors and do not induce cell death. Also in vitro, the maturation of B cell precursors was not affected by KMC. KMC does not inhibit the proliferative response to IL-3 or IL-2. These results suggest that KMC is selectively affecting B cell lymphopoiesis, possibly acting on the IL-7 signaling pathway, opening new perspectives for a potential therapeutic usage of Kb derived drugs.