Innovative approaches addressing the elevated human immunodeficiency virus (HIV) risk among men who have sex with men (MSM) or transgender women (TGW) migrants in South Africa are urgently needed. We sought to present the acceptability, feasibility and preliminary efficacy of 'Externalize and Mobilize!', a multi-session arts- and theatre-based HIV prevention group intervention for MSM and TGW migrants in South Africa. Fourteen participants--MSM (n = 7; 50%), genderqueer/nonbinary persons (n = 4; 29%) and TGW (n = 3; 21%)--in Cape Town were recruited and enrolled in the intervention and administered pre- and post-intervention assessments of HIV knowledge, HIV risk-reduction self-efficacy, stigma and resilience. The intervention, delivered over 4 days, was completed by all 14 participants. Scores on HIV knowledge and HIV risk-reduction self-efficacy were statistically significantly higher at post-intervention compared with pre-intervention. Additionally, participants responded affirmatively (i.e. 'Agree' or 'Strongly agree') on all items assessing intervention acceptability. Findings demonstrate the high acceptability, feasibility and preliminary efficacy of an arts- and theatre-based intervention for increasing HIV knowledge and HIV risk-reduction self-efficacy among MSM and TGW migrants in South Africa. This study provides further support for the use of creative and innovative interventions to address entrenched HIV disparities in South Africa.