The major role of self-directed learning (SDL), a sub-division of autonomy, in successful learning at distance education has been confirmed by various studies. Although learners pass General English courses before studying any ESP courses at distance education of Iran, they usually lack the preliminary skills for independent language learning. The current study aimed to explore the effect of self-directed training (SDT) on ESP learners' self-directed learning readiness (SDLR) and their academic achievements in ESP courses. The results revealed that SDT enhanced ESP learners' SDLR and their academic achievements in the corresponding ESP courses. Moreover, no difference was observed between the male and female learners' SDLR and ESP scores. The findings imply that an appropriate training is needed to improve learners' SDLR. It can contribute to a successful ESP learning at distance learning.