This study explored interest in injectable PrEP (I-PrEP) and willingness to participate in clinical trials testing new biomedical HIV prevention strategies among men and transfeminine persons who have sex with men (MSM & TGP), using data collected in the HIV Prevention Trials Network (HPTN) 075 study, which took place at sites in Kenya, Malawi, and South Africa. Data result from a survey among 267 18-44 years old HIV negative participants, complemented with semi-structured interviews with 80 purposively recruited persons. Correlations coefficients were calculated to identify demographic and psychosocial factors associated with interest in I-PrEP. Qualitative interviews were analyzed using concept-driven and subsequent data-driven coding. Most surveyed participants expressed an interest in I-PrEP. Quantitatively, only being interested in other HIV prevention measures was associated with interest in I-PrEP. Qualitatively, most participants preferred I-PrEP to O-PrEP and remained interested in I-PrEP despite barriers such as the somewhat invasive nature of the procedure and potential side effects of I-PrEP. Interest in I-PrEP was driven by the possibility of avoiding sexual or HIV stigma. Access to healthcare and altruism-such as assisting in the development of new HIV prevention methods-positively impacted willingness to participate in clinical trials. With I-PrEP favored by most participants, it is potentially a critical tool to prevent HIV infection among MSM & TGP in sub-Saharan Africa, with the mitigation of stigma as a major advance. Recruitment of MSM & TGP in biobehavioral clinical trials seems feasible, with altruistic reasons and receiving I-PrEP and free medical care as major motivators.