This paper examines the evolution of interpreters’ perception and application of (codes of) ethics and its impact on the making of a profession in China’s mainland since 1949, from both a sociological and a historical perspective. Using Bourdieu’s theory of practice as an analytical tool, and drawing on email interviews with interpreters, autobiographies and narrations produced by interpreters and institutional documents, in addition to surveying the relevant literature, the author explores how and why the five core ethical principles for interpreters – competence, integrity, fidelity, neutrality, confidentiality – were understood and practised in different ways by interpreters in the past 70 years. The findings indicate that most of these five principles were differently perceived and applied by interpreters in the three historical periods between 1949 and 2019 due to interpreters’ different levels of capitals, state of habitus, and interpreting as, respectively, a heteronomic field (1949–1978), a field moving towards professional autonomy (1979–2009), and a field likely to become a (sub)field of the rising language service industry (2010–2019).