Sexuality education (SE) is a fundamental right and can be acquired through different sources. In a cross-sectional online study with Spanish and Portuguese participants (N = 595), we examined differences between formal traditional sources (i.e., mandatory SE received in schools), formal modern sources (e.g., SE received in courses), informal traditional sources (e.g., talks with friends and family), and informal modern sources (e.g., pornography and online content) and their contribution to sexual health and well-being outcomes. Results showed that topics related to sexual and reproductive health were among the most addressed. Nearly all participants received SE from informal sources, whereas more than two-thirds received SE from formal traditional sources. Some differences between Spain and Portugal emerged. Results of a linear regression model showed that participants who perceived more influence from formal traditional sources reported using condoms more often, were more focused on disease prevention, and enacted more sexual health communication, but were also less sex-positive. Participants who perceived more influence from both types of informal sources attributed more importance to SE topics but reported having condomless sex more frequently and were more focused on pleasure promotion. Still, participants who perceived more influence from informal traditional sources also endorsed more internal/external consent, were more sexually satisfied, were more sex-positive, and enacted more sexual health practices. Lastly, participants who perceived more influence from informal modern sources were also more likely to have been diagnosed with an STI. Only a small proportion of participants received SE from formal modern sources and had to be excluded from this analysis. Taken together, our findings highlight the need to consider different sources for a more comprehensive and inclusive SE.