This study investigates temporal changes in Iranian EFL learners' L2 motivation and the possibility of predicting their motivated learning behaviour, ideal and ought-to L2 selves and L2 learning experience in light of Dörnyei's (2005) L2 motivational self-system framework. To this end, 1,868 learners of four educational levels (i.e. junior high and high school levels, BA/BSc and MA levels) filled out the questionnaire developed by Taguchi et al. (2009). The results of the one-way ANOVA revealed a higher motivational disposition for secondary school students and an age-related decline specifically concerning preventional-focus variables. Moreover, the results of the regression analyses showed that different factors predicted the three components of L2 motivational self-system and intended effort of the four educational groups. Most of the predicting factors of students' ideal L2 self, learning experience and motivated behaviour had a promotional focus whereas preventional-focus variables were among predictors of students' ought-to L2 self.