A semi-solid lubricant composition for transmission elements which is excellent in lubricity, antiwear properties, and energy-saving performance, has high reliability, and is for use as a turbine oil, machine tool oil, metal working oil, plastic working oil, cutting oil, compressor oil, vacuum-pump oil, electrical-contact oil, grease, or machine oil; and a mechanical system provided with the composition. The composition, which reduces the wear of sliding parts of a transmission element, comprises: an amide compound having one or two amide groups and forming a three-dimensional network structure; and a liquid base oil ingredient having a dynamic viscosity at 100° C. of 25 mm2/s or lower and a viscosity index of 120 or higher. The composition contains substantially no ingredients other than the amide compound and liquid base oil ingredient. The mechanical system has a transmission element including sliding parts which are provided with the semi-solid lubricant composition for transmission elements.