Psychiatry, psychology and psychotherapy played an important role in attempts to regulate and rehabilitate New Zealand men imprisoned for sodomy and indecent assault between 1910 and 1960. Little attention has, so far, been paid to the specific psychological ‘treatment’ of such incarcerated men in the international context, but New Zealand’s archives offer-up much valuable detail. This article adopts a Foucauldian approach and explores shifting epistemic beliefs alongside the specific practices of key medical officials, and it considers how prisoners’ subjectivities were shaped in the process. Attempts to displace homoerotic desire gradually gave way to the articulation of same-sex sexuality. New possibilities emerged: when the psychologising of homosexuality in prisons opened the door to self-expression it showed an affinity with the organised resistance of the 1970s.