Background <p>Uterine after pain is a common yet under-addressed postpartum complaint. This study aimed to investigate whether early postpartum supplementation with vitamins D and E could reduce the intensity and duration of uterine after pain in multiparous women.</p> Methods <p>This double-blind, parallel-group randomized clinical trial was conducted between October and December 2022 at Shahid Mobini Hospital in Sabzevar, Iran. One hundred eligible multiparous women were randomly assigned to receive either eight capsules containing 100&#xa0;mg of vitamin E and 400 IU of vitamin D over the first 48&#xa0;h postpartum or matched placebo capsules. Pain intensity was assessed via the visual analog scale (VAS), beginning 2&#xa0;h after delivery and subsequently at 6-hour intervals across eight time points. The duration of pain was measured via the Cox Menstrual Symptom Scale (CMSS). Data analysis was performed via SPSS version 16, with statistical significance set at <i>P</i> &lt; 0.05.</p> Results <p>No significant differences in pain intensity or duration at baseline were detected between the groups (<i>P</i> = 0.58 and <i>P</i> = 0.06, respectively). From the third time point onward, participants in the intervention group reported significantly lower pain intensity than did those in the placebo group (<i>P</i> &lt; 0.001). A similar trend was observed for pain duration, with a statistically significant reduction starting from the second time point in the intervention group (<i>P</i> &lt; 0.001).</p> Conclusion <p>Supplementation with vitamins E and D during the early postpartum period may serve as a safe, effective, and accessible strategy for reducing the intensity and duration of uterine after pain in multiparous women. These findings support the integration of targeted micronutrient therapy into postpartum pain management protocols.</p> Trial registration <p>Iranian Registry of Clinical Trials (IRCT): IRCT20220313054270N1.</p>