According to an aspect of the present invention, there is provided a method, system, and computer program product for version conflict checking of installable units (IUs). The method includes receiving a request for version conflict checking of specified IU, the request including a version dependency relationship between IUs that are in a dependency relationship with the specified IU. A version dependency relationship between installed IUs is obtained. The version dependency relationship between the installed IUs is updated according to the version dependency relationships between the IUs that are in a dependency relationship with the specified IU. It is checked whether the specified IU has a version conflict with the updated version dependency relationship between the installed IUs.