In order to pass more than one argument to the lessc compiler you need to use the option argument for each variable, for example lessc –modify-var=”bgColor=purple” –modify-var=”bodyColor=aqua” custom.less test.css Notice the “–modify-var” option being passed twice, this is because there is no separator https://github.com/less/less.js/issues/731#issuecomment-28477515