The invention relates to a miniature kinetic energy harvester for generating electrical energy, comprising a support, a first element having walls surrounding at least one cavity, at least one spring mounted between the first element and the support, the spring being arranged so that the first element may be brought into oscillation relative to the support according to at least one direction of oscillation, a transducer arranged between the first element and the support for converting oscillation of the first element relative to the support into an electrical signal, at least one second element housed within the cavity and mounted to freely move within the cavity relative to the first element so as to impact the walls of the cavity when the harvester is subjected to vibrations.