Writing and its role in English as a foreign language (EFL) context has been one of the primary areas of focus for many years. The present study examined the effects of mobile-based concept mapping on EFL learners' writing fluency and motivation. To fulfill the objective, 70 upper-intermediate level Persian EFL learners were assigned into one experimental and one control conditions, each including 35 participants. The experimental condition's participants received instruction through mobile-based concept mapping while the students of the control condition did not receive any instruction and were just required to discuss the topics and write about them traditionally. The findings of the study revealed that mobile-mediated concept mapping was effective for EFL students' writing fluency. Moreover, the results indicated that mobile-based concept mapping was beneficial for learners' writing motivation.