Introduction: Telephone-based smoking cessation support is among the strategies considered effective for helping motivated smokers quit. The Tabac Info Service (TIS, 39 89) hotline, established in 1998, has undergone changes, and its effectiveness has been evaluated. Methods: Since April 2013, all callers to 39 89 who spoke with a tobacco specialist have been contacted again six months later. The primary objective is to measure the smoking abstinence rate and associated factors. Results: Between September 2012 and July 2014, 13,161 smokers or smokers attempting to quit who called 39 89 were assisted by a TIS tobacco specialist. Young people, the unemployed, and manual laborers are underrepresented compared to the general French smoking population. Among those who agreed to be contacted six months later, more than one in five (21.9%) reported being smoke-free for at least seven days at the time of follow-up (those who could not be reached or who refused to participate at six months were considered smokers). The abstinence rate was 32.4% among smokers attempting to quit and 19.3% among other smokers. This rate was lower among the most dependent smokers and increased with the number of follow-up interviews conducted by a tobacco specialist on the helpline. Finally, more than three-quarters of respondents at six months reported that TIS had helped them in their quit attempt. Discussion: The results, consistent with European and American data, suggest that 39 89 is effective, particularly for smokers attempting to quit at the time of their first contact with the service. With a view to reducing social health inequalities, this telephone service—which is virtually free for its users—could be promoted more actively among job seekers and blue-collar workers, who are underrepresented among current users of 39 89.