This study explored the effects of using e-portfolios on English as a foreign language (EFL) learners’ speaking fluency, as well as their opinions regarding e-portfolio implementation in their program. Sixty EFL students participated in a mixed-methods sequential study and were assigned randomly to an experimental (e-portfolio) group and a control (non-e-portfolio) group. Whereas the experimental group kept portfolios on a social network (Eitaa), the control group presented their speaking activities in the classroom. The speaking fluency of both groups was assessed through pretest and posttest structured interviews, and four aspects of their fluency (speech rate, articulation rate, phonation time ratio, and silent pause rate) were analyzed using the PRAAT and SPSS software. Also, in the subsequent qualitative phase, 20 learners from the e-portfolio group took part in a semistructured interview. According to the quantitative data analysis, speaking fluency increased significantly in the e-portfolio group, and the gain was statistically higher than that of the non-e-portfolio group. The qualitative data analysis revealed 3 main themes of social-emotional and metacognitive benefits, social media portfolio challenges, and fluency in speaking. The findings encourage educators to consider using e-portfolios as a potential medium to improve second/foreign language (L2) learners’ speaking fluency.