Guided by Grolig (2020)’s bioecological perspective, this study examined the effects of a shared book reading intervention for ethnic minority kindergarteners learning Chinese as a second language (L2) in Hong Kong. A quasi-experimental study was conducted with 365 kindergarteners across three groups: an experimental group of L2 Chinese children receiving an 8-week intervention, and two control groups (L2 and L1 Chinese children) receiving regular instruction. Four major findings emerged: (1) The experimental group showed significant improvement in L2 Chinese reading subskills. (2) Low and mid-level L2 learners gained more from the intervention than high-level learners initially. (3) High-level L2 learners performed comparably to L1 peers in post-test Chinese metalinguistic awareness. (4) L2 children’s reading proficiency was influenced by home literacy environment factors, including father’s education, parents’ Chinese proficiency, and number of books at home.