Naldemedine is the newest orally available, peripherally selective μ-opioid receptor antagonist blocker approved for opioid-induced constipation (OIC) treatment in adult patients. On the other hand, some patients have insufficient OIC control even with naldemedine. Thus, this retrospective study was conducted to identify factors affecting the effect of naldemedine. The participants were 210 patients who had received naldemedine at our institute between June 2017 and August 2019. Variables associated with alleviation of OIC were extracted from clinical records and used for regression analysis. The effect of naldemedine was determined according to the degree of constipation. The degree of constipation was categorized as grade 0 - 2 with reference to the CTCAE version 5.0. Multivariate ordered logistic regression analysis was conducted to identify factors affecting the effect of naldemedine. Use of naldemedine within 2 days of opioid initiation [odds ratio (OR) =0.346, 95% confidence interval (CI) =0.173-0.693; P = 0.003], concomitant use of anticholinergics (OR = 2.033, 95% CI = 1.150-3.594; P = 0.015), tramadol (OR = 0.488, 95% CI = 0.250-0.953; P =0.036), and chronic non-cancer pain (OR = 0.429, 95% CI = 0.197-0.937; P = 0.034) were identified as significant factors related to the effect of naldemedine.