The French Antilles (Martinique, Saint Martin and Guadeloupe) and French Guiana are the French territories most affected by the HIV epidemic. Some population groups such as men who have sex with men (MSM), especially those involved in transactional sex, are thought to be particularly vulnerable to HIV but few data exist to help characterize their health-related needs and thus implement relevant prevention interventions. To fill this knowledge gap, we used data collected from an HIV/AIDS Knowledge, Attitudes, Behaviours and Practices survey conducted in 2012 among MSM living in the French Antilles and French Guiana and recruited through snowball sampling. Our objectives were to compare social and demographic characteristics and sexual behaviours between MSM engaging in transactional sex and MSM not engaging in transactional sex and to identify factors associated with transactional sex involvement using a logistic regression model. A total of 733 MSM were interviewed, 21% of whom reported to undergo transactional sex. Their behaviour and social and demographic characteristics were different from other MSMs' and they were more exposed to factors that are recognized to potentiate HIV vulnerability, at the individual, community, network and structural levels. The variables positively associated with sex trade involvement were having ever consumed drug (OR=2.84 [1.23-6.52]; p=.002), having a greater number of sex partners than the median (OR=8.31 [4.84-14.30]; p<.001), having experienced intimate partner violence (OR=1.72 [0.99-3.00]; p=.053) and having undergone physical aggression because of sexual orientation (OR=2.84 [1.23-6.52]; p=.014). Variables negatively associated with sex trade involvement were being older (OR=0.93 [0.90-0.97] per year; p=.001), having a stable administrative situation (OR=0.10 [0.06-0.19]; p<.001), having a stable housing (OR=0.29 [0.15-0.55]; p<.001) and being employed full-time (OR=0.29 [1.23-6.52]; p=.002).