Social networking service platforms and social media have generated a significant amount of discussion and debate regarding their use in second or foreign language learning. However, leveraging digital tools with pedagogical constructs to enhance accessibility and engagement in teaching and learning English idiomatics has not received equal attention. Consequently, discovering new modes of learning in the formulation and implementation of English idiomatics instruction in the modern digital age is a must. This study investigated Chinese EFL learners' development of idiomatic competence. It examined English vivid phrasal (VP) idiom learning in classrooms supporting WeChat use vis-à-vis the classrooms supporting traditional modes of language instruction without WeChat. It also explored the extent to which WeChat-enhanced instruction can affect learners' motivation, attitude, collaboration, and experience. The participants of this study were 55 first-year English major students who took part in an intensive, eight-week idiom-training module. A pre- /post-test and a questionnaire were used to uncover how a WeChat-driven learning environment can mediate the way students acquired Post-Lexical Level (PLL) VP idioms and what their general perceptions towards using WeChat in the idiom-oriented activities were. The results indicated that there was a statistically significant difference in achievement between the WeChat-enhanced group and the traditional face-to-face group. Analysis of data further revealed that peer interactions supported by WeChat are likely to be essential learning constructs in furthering idiomatic competence development.