Introduction: Longitudinal melanonychia (LM) is a common clinical condition that is mostly identified by the presence of longitudinal, demarcated, and pigmented bands on the nail. Different benign or malignant pathologies can present with longitudinal melanonychia. Therefore, we aimed to investigate the frequency of dermoscopic features of LM in patients with LM referred to dermatology clinics in Guilan, Iran. Materials and Methods: This case-series study was conducted on 30 patients with LM who were referred to Besat clinic and Razi hospital, Rasht, Iran, from March 2022 to August 2022 with a complaint of LM. Demographical data and dermoscopic findings of patients were collected and analyzed using SPSS version 21. The LM and dermoscopic features were investigated using a dermatoscope (HEINE IC1, HEINE Optotechnik, Germany). Results: Out of 30 patients, 24 patients were female and 6 patients were male with a mean age of 30.08 ± 14.31 years old. Among these patients, five patients had a family history of LM, one patient with melanoma had Hutchinson’s sign, and three patients had pseudo-Hutchinson’s sign. The mean width of lesions of the nail was 2.42±2.12 mm with a mean time of onset of 7.42 ± 7.12 months. Also, the majority of the involved site of LM was hand (26.6%). Conclusion: According to our study, LM was more frequent in females and the trauma-related lesions of the nail were the most common dermatological findings among the patients.