Aim <p>Gambling is increasingly accessible because of online platforms and the expansion of legalized sports betting. Earlier gambling initiation has been associated with greater risks of later gambling-related harm. This study examined generational differences in the age of gambling onset and whether patterns differed between individuals who bet on sports and those who gamble but not on sports.</p> Subject and methods <p>Data were drawn from a US online panel sample of more than 1600 adults who reported gambling participation in the past 6 months. Self-reported age of gambling initiation, sports betting participation, and generational cohort differences were examined to assess whether associations between sports betting and onset have changed over time.</p> Results <p>Sports bettors reported earlier gambling initiation than non-sports gamblers, although this association varied across generational cohorts. In older cohorts, individuals who bet on sports began gambling substantially earlier, whereas in more recent cohorts this difference was markedly smaller. The proportion of gamblers who participated in sports betting also increased across cohorts, shifting from a minority to a majority practice among younger adults.</p> Conclusions <p>Gambling initiation patterns may be changing alongside the normalization and mobile availability of sports betting. Monitoring cohort differences in gambling onset and sports betting participation may help inform targeted public health prevention and harm-reduction strategies.</p>