Background: It is a priority to develop population-based strategies for reducing barriers to smoking cessation among low-income populations. Harnessing secondary transmission such as interpersonal communication (IC) has helped to reduce tobacco use, but there is a dearth of quasi-experimental research that examines IC and the full spectrum of smoking cessation behaviors, particularly in the context of population-level programs. Aims: Using quasi-experimental methods, we examined IC in response to a population-level intervention and its impact on the full spectrum of smoking cessation outcomes among low-income smokers. Method: We used propensity score matching; three different propensity score matching procedures were used to estimate and approximate experimental effects. We assessed four cessation outcomes: utilization of a free tobacco quitline (QL), making a quit attempt, and being smoke-free for 7 and 30 days at follow-up. We also examined predictors of IC. Results: IC was significantly related to QL utilization (effect sizes ranging from 0.135 to 0.166), making a quit attempt (effect sizes ranging from 0.115 to 0.147), being smoke-free for 7 days (effect sizes ranging from 0.080 to 0.121), and being smoke-free for 30 days at follow-up (effect sizes ranging from 0.058 to 0.082). Program-related and participant characteristics predicted IC, such as receiving emotional direct mail materials and living with a fellow smoker. Discussion: IC in response to a population-based program affected the cessation process, and IC had a marked impact on sustained cessation. Conclusion: Population-based programs should aim to harness psychosocial dynamics such as IC to promote sustained cessation among low-income populations.