Background: A fungal infection of the nail unit, onychomycosis (OM) is brought on by dermatophytes, yeast, and non-dermatophyte moulds (NDM). It is the most prevalent nail infection in clinical practice, occurring at 5.5% of the time worldwide. Objective: This study aimed to evaluate the role of dermoscopy in diagnosis of finger and toenail onychomycosis through correlating its finding with mycological study results. Patients and methods: The current study was carried out on 45 patients with nail abnormality (clinically) suggesting onychomycosis. They were divided into three equal groups according to site of infection (finger, toe and both). Dermoscopic examination and taking photographs were taken to detect different clinical and dermoscopic patterns. Nail scrapings were collected and examined using direct microscopic examination with KOH (20%) and cultured on SDA media to detect causative organism. Results: Of all studied groups, female gender showed the highest prevalence in all studied groups representing 80%, 66.7% and 66.7% in group I, II and III respectively. The mean ages of the three groups (I, II and III) were 43.5 ± 12.3, 39.3 ± 12.3 and 47.6 ± 13.1 years respectively. Thumb was the most common affected finger in groups I and III (finger affection) by 53.3%, while the big toe was the commonest affected toe in groups II and III by 100% and 73.3% respectively. According to occupation, 51.1% of all cases were housewives. Conclusion:  Onychomycosis had high prevalence in female gender, middle age, housewives and farmers. Thumb and big toenails were the most common affected nails. According to clinical types of onychomycosis, DLSO was the commonest clinical type between all groups of onychomycosis except in group III (toe affection) that PSO was the commonest clinical type.  According to dermoscopic patterns, brown and black pigmentation, toe jagged proximal edge with spikes and Subungual hyperkeratosis was the commonest dermoscopic patterns in groups I, II and III respectively.