Background: Opioid analgesics and psychotropic drugs (medical narcotics) are essential for treating pain and psychiatric disorders. Unlike tiered classification systems used globally, Korea uniformly classifies these medications with illicit drugs under a single narcotics category. This creates misunderstandings among patients and physicians. This study investigates perceptions of medical narcotics, assesses awareness of the Narcotics Information Management System (NIMS), and proposes strategies to prevent misuse and abuse. Methods: A cross-sectional survey from September 2021 to June 2025 enrolled 322 patients prescribed opioid analgesics or psychotropic drugs for ≥180 days per year and surveyed 300 physicians via email. Categorical variables were expressed as frequencies (percentages) and compared using a Chi-square test. Multivariable logistic regression adjusted for age and gender was performed and subgroup analyses were performed, including by patient education level (using ANOVA and Bonferroni-corrected post hoc comparisons) and treatment duration, alongside physician specialty and affiliation. Results: Significant perception differences emerged between patients and physicians. The largest perception discrepancy was in distinguishing medical narcotics from illicit drugs (48.8 percentage point difference; 9.9% vs. 58.7%; p < 0.001). The NIMS Data Service awareness was lowest in both groups (patients 14.6% vs. physicians 34.3%). In multivariable-adjusted analysis, perception differences were greater in those over 60 years old. In the subgroup analysis, patient-physician perception gaps, as reflected by odds ratios, were greater in patient-groups with shorter treatment duration (<36 months) compared to those with longer treatment duration (≥36 months). Conclusions: Perceptions of opioid analgesics and psychotropic drugs are significantly different between patients and physicians. Both groups showed limited awareness of medical narcotics and the narcotics control system. Targeted educational initiatives are crucial for both patients and physicians to bridge existing perceptual and knowledge gaps, especially for patients aged 60 years or older and patients with shorter medical narcotics treatment duration (less than 36 months).