Mobile devices are considered as the most widely used information and communication technologies. They have provided great advantages in language learning. This study reports a meta-analysis of the effectiveness of using mobile devices on vocabulary learning. A meta-analysis was conducted on research that compared the outcomes from students learning vocabulary using mobile devices to those learning vocabulary using traditional ways of learning. The meta-analysis examined how effect sizes varied based on learners' age, type of vocabulary learning (receptive or productive), and aspects of vocabulary used (form, meaning, and use). This meta-analysis examined the effect of using mobile devices on vocabulary learning by reviewing 16 studies involving 986 participants. The use of mobile devices in learning vocabulary was associated with greater achievement in comparison with traditional ways. The findings of the meta-analysis indicate a medium effect of using mobile devices on vocabulary learning (g = 0.67). Major findings of the current meta-analysis include the following: (a) Mobile devices have moderate effect sizes on both ways of vocabulary learning (productive and receptive), (b) adult learners get benefit from using mobile devices in vocabulary learning better than young learners, and (c) mobile devices have moderate effect on all aspects of vocabulary learning.