This study examined the effects of individual difference (ID) factors on changing pragmatic abilities among L2 learners of English. Participants were 48 Japanese EFL students in an English-medium university in Japan. They completed a pragmatic speaking test (k=12) that assessed their ability to produce two speech acts: requests and opinions, in high- and low-imposition situations. The measure was given three times during one academic year. Speech acts were evaluated for appropriateness and fluency. Three ID factors (proficiency, orientation towards English study, and lexical access skill) were measured, and their effects on changes in appropriateness and fluency of speech act production were assessed. Results revealed significant effects of individual factors on pragmatic change, but the effects appeared differently between appropriateness and fluency.