Doping in sport remains a persistent global challenge, eroding sporting integrity, athlete welfare, and public trust. Over the past 25 years, psychological research on doping has progressed from individual-level explanations to embracing more nuanced, systemic perspectives. This narrative review synthesises key developments in the field, addressing definitional ambiguities, dominant theoretical frameworks, and emerging trends in anti-doping research. Social cognitive theories have been particularly influential, with meta-analytic evidence highlighting psychosocial predictors such as attitudes, perceived norms, and supplement use. However, the field remains constrained by a reliance on proxy measures of behaviour and a narrow conceptualisation of doping, typically defined as the use of prohibited substances. This review calls for a broader understanding of the behavioural violations that constitute doping, alongside a shift toward systemic thinking and transdisciplinary collaboration. It emphasises the need to engage with the lived experiences of athletes and support personnel, and to design behaviourally targeted, context-sensitive interventions. Meaningful progress depends not only intervention content but also on their alignment with the lived realities of those involved in sport. Future research priorities include co-created, theory-informed interventions, longitudinal designs, and globally inclusive agendas that reflect diverse voices and sporting cultures. Sustained investment and stronger alignment between research, policy, and practice are essential to protect sport integrity and safeguard athlete and support personnel welfare.