Pacifier use at sleep time decreases sudden infant death syndrome (SIDS) risk. It is yet unclear whether pacifier use can modify the impact of other sleep-related factors upon SIDS risk. The objective of this study was to examine the association between pacifier use during sleep and SIDS in relation to other risk factors and to determine if pacifier use modifies the impact of these risk factors. Data source was a population based case-control study of 260 SIDS deaths and 260 matched living controls. Pacifier use during last sleep decreased SIDS risk (aOR 0.30, 95% CI 0.17-0.52). Furthermore, pacifier use decreased SIDS risk more when mothers were ≥20 years of age, married, nonsmokers, had adequate prenatal care, and if the infant was ever breastfed. Pacifier use also decreased the risk of SIDS more when the infant was sleeping in the prone/side position, bedsharing, and when soft bedding was present. The association between adverse environmental factors and SIDS risk was modified favorably by pacifier use, but the interactions between pacifier use and these factors were not significant. Pacifier use may provide an additional strategy to reduce the risk of SIDS for infants at high risk or in adverse sleep environments.