Background: Few studies have tested the effect of a motivational telephone intervention from a gambling operator to clients with high-risk gambling practices. This study aimed to study subsequent gambling abstinence, limit setting and self-exclusions post-intervention, compared to controls.Methods: The study assessed a motivational, personalized telephone intervention by the state-owned Swedish gambling operator AB Svenska Spel. Clients successfully reached with the telephone intervention (n=1,420) were compared to clients who could not be reached (n=1,504). Gambling practices during eight weeks pre-intervention were assessed, and outcome measures were gambling abstinence, limit setting and self-exclusion four weeks post-intervention.Results: The telephone intervention was associated with increased gambling abstinence weeks 2-4 post-intervention (24 vs 20 percent, p=0.02), limit settings (10 vs 5 percent, p<0.001) and self-exclusions (11 vs 8 percent, p<0.01), but not significantly associated with full week 1-4 abstinence (18 vs 15 percent, p=0.07). In unadjusted analyses of sub-groups, significant associations of the intervention with full gambling abstinence were seen in online casino/bingo gamblers (19 vs 14 percent, p<0.01). In logistic regression, controlling for different gambling types, effects of the intervention were seen in the highest sub-segment with respect to gambling losses.Conclusions: A personalized motivational telephone intervention to high-risk gamblers, delivered by a gambling operator, is promising. Effects are likely more pronounced in players of online chance-based games, and in gamblers with high pre-intervention losses.