Patients and Methods: This study was a randomized clinical trial with the control group. A total of 158 mothers in postpartum period (with certain inclusion criteria) were enrolled in the study and assigned randomly to two groups of control and intervention. Lavender fragrance (made by Barij Essence Pharmaceutical Co.) was used by participants in the intervention group nightly before sleeping. The fragrance was dropped on cotton balls, which were placed on a cylindrical container at mothers’ disposal. Keeping the container at a projected distance of 20 cm, the participants inhaled 10 deep breaths and then the container was placed beside their pillow until morning. This procedure was done 4 times a week for 8 weeks. For the control group, the same intervention was done with the placebo. The instrument for collecting data was Pittsburgh sleep quality index, which was completed at the baseline, fourth, and eighth weeks after the intervention. Data were analyzed using independent t test and repeated measures analysis of variance calculated by SPSS16.