<p>Sleep-related disturbances, including poor sleep quality and insomnia, are prevalent during pregnancy and the postpartum period. These disturbances are associated with various adverse outcomes. This study aimed to evaluate the impact of sleep hygiene education on insomnia severity and sleep quality among pregnant women. This study was designed as a randomized controlled trial with two parallel groups. It was conducted with a sample of 70 pregnant women enrolled in comprehensive health centers in Nahavand City, Hamedan, during the years 2023–2024. A 4- and sixfold random block method was employed to assign participants to the intervention and control groups. In addition to receiving routine care, the intervention group participated in four sleep hygiene education sessions conducted in groups of five. In contrast, the control group received only routine care. Prior to the study’s initiation and 4&#xa0;weeks after the completion of the educational sessions, participants from both groups completed the Sleep Hygiene Index (SHI), Insomnia Severity Index (ISI), and Pittsburgh Sleep Quality Index (PSQI). Data were analyzed using Stata-13 software, with a significance level set at less than 0.05 for all statistical tests. In the post-intervention stage, after controlling for the influence of pre-intervention scores, the PSQI score in the intervention group decreased compared to the control group (mean differences (MD) =  − 2.26; 95% confidence interval (CI): − 3.28 to − 1.24; <i>p</i> &lt; .001) and Cohen’s <i>d</i> equal to 1.07. The mean SHI score in the intervention group showed a significant decrease of 6.23 scores compared to the control group (<i>p</i> &lt; .001). Additionally, the mean ISI score in the intervention group decreased by 1.26 points relative to the control group at with the moderate effect size calculated at 0.75 (<i>p</i> = .002). Sleep hygiene education can enhance sleep hygiene, alleviate insomnia, and improve sleep quality in pregnant women during the third trimester.</p>