Few studies have investigated the development of L2 complaints. This paper reports on a longitudinal study of L2 complaints produced by Chinese university English learners based on their performance of a discourse completion task consisting of 18 complaint scenarios in terms of power (+P, =P, −P) and social distance (−D, =D, +D), supplemented by a delayed retrospective verbal report. Data were collected twice, over two academic years. The results indicate that students in these two ‘phases’ showed broadly similar patterns of sociopragmatic competence in terms of their ability to calibrate complaints to complainees’ (addressees’) position on power and social distance continua. However, as to internal modifications, learners in Phase 2 used significantly more lexical and syntactic downgraders than in Phase 1 at all levels of power and social distance except for syntactic downgraders at +D and =D; they only used significantly more lexical upgraders at −D. As for external modifications, the findings also showed significantly different patterns in the use of pre-moves at all levels and post-moves at all levels except at −P. Increase of English proficiency and a certain degree of explicit pragmatic instruction may have contributed to Chinese EFL learners’ pragmatic development. Implications for pragmatic instruction are also discussed.