INTRODUCTION: This pilot randomized controlled trial sought to evaluate whether an online intervention for problem gambling could lead to improved gambling outcomes compared to a no intervention control. Participants were recruited through a crowdsourcing platform. METHODS: Participants were recruited to complete an online survey about their gambling through the Mechanical Turk platform. Those who scored 5 or more on the Problem Gambling Severity Index and were thinking about quitting or reducing their gambling were invited to complete 6-week and 6-month follow-ups. Each potential participant who agreed was sent a unique password. Participants who used their password to log onto the study portal were randomized to either access an online intervention for gambling or to a no intervention control. RESULTS: A total of 321 participants were recruited, of which 87% and 88% were followed-up at 6 weeks and 6 months, respectively. Outcome analyses revealed that, while there were reductions in gambling from baseline to follow-ups, there was no significant observable impact of the online gambling intervention, as compared to a no intervention control condition. CONCLUSIONS: While the current trial observed no impact of the intervention, replication is merited with a larger sample size, and with participants who are not recruited through a crowdsourcing platform.Trial registration: ClinicalTrials.govNCT03124589.