Previous research suggests that the presence of other gamblers in a gambling venue intensifies individual gambling behavior. To study such potential social facilitation among gamblers, we conduct a large-scale analysis of more than one million gambling sessions using player tracking data of the Norwegian gambling operator Norsk Tipping. In particular, we empirically assess the existence and strength of this facilitation, and how it manifests in differently utilized gambling venues. In our study, we control for (i) each individual's co-gamblers (frequent vs. occasional co-gamblers) and for (ii) the magnitude of individual's social participation (social seeking vs. social avoiding gamblers). We find that gamblers stake more money and play longer sessions the more crowded the venues get and that social avoiding gamblers gamble more when they play with their most-frequent co-gambler. Interestingly, our results strongly indicate that social avoiding gamblers are more susceptible to social facilitation than gamblers who are familiar with crowded gambling venues. Overall, our research is the first large-scale study of social facilitation among gamblers introducing a novel framework to empirically measure this effect. We believe that our work will have important practical implications for both gambling behavior researchers as well as the gambling industry in designing and evaluating responsible gambling tools.