The practice of sex with casual partners without the use of adequate prevention in the period of social distancing due to the COVID-19 pandemic among men who have sex with men (MSM) can expose them to the risk of infection by the HIV virus. To assess this, we conducted an online survey in April and May 2020 in the entire national territory of Brazil and Portugal. We used the snowball technique for sampling, associated with circulation in social networks, totaling 2934 participants. Bivariate and multivariate logistic regression was used to produce the adjusted Odds Ratio (aOR). Eight-hundred-and-forty-two (28.7%) MSM presented at-risk sexual exposure in this period. In general, the types of sexual practices that most increased the chances of sexual exposure were having multiple partners (aOR:14.045); having practiced chemsex (aOR:2.246) and group sex (aOR:2.431), as well as presenting a history of at-risk sexual exposure (aOR:5.136). When we consider each country separately, the chances are increased in Brazil since the probability of the outcome was increased in those who practiced group sex (aOR:5.928), had multiple partners (aOR:19.132), and reported a sexual history of at-risk exposure (aOR:8.861). Our findings indicate that practices that are classically associated with greater chances of engaging in risky sexual exposure to HIV infection were the factors that most increased the chances of acquiring the virus in the pandemic context.