Few studies have investigated the discourses and ideologies around parents' enrollment decisions in Chinese-English immersion contexts, and how these discourses and ideologies affect their involvement with their children' bi/multilingual development. Conducted in a K-5 50/50 one-way Mandarin immersion school, this paper focuses on ethnographic interviews with parents that represent different social and cultural backgrounds. Findings demonstrate multiple ways that parents support and invest in their children's bi/multilingual development. Findings also reveal that the ideology of neoliberal multilingualism and multiculturalism permeates parents' decision-making, expectations, and investment. This ideology motivates parents to actively advocate for this school's survival and combat with the local discourse of monolingualism, which creates a space with a humanitarian emphasis with multiculturalism but also shapes the school space in a certain way. Meanwhile, tensions exist among different parent groups in terms of their perceptions toward the ultimate benefits of this immersion school and the unbalanced parental influence on local language policymaking. This case study aims to investigate the discourses and parents' ideologies in Chinese immersion education, and to offer some implications for language planning in one-way foreign language immersion contexts.