Three cases of proximal subungual onychomycosis due to Fusarium oxysporum, including a patient with a fingernail infection, are described. All patients were immunocompetent and presented with acute paronychia associated with proximal or total leukonychia of the affected nails. Nail avulsion followed by topical treatment produced clinical and mycological cure. The literature on Fusarium onychomycosis is discussed. The combination of proximal subungual onychomycosis with subacute or acute paronychia involving fingernails or toenails is highly suggestive of Fusarium sp.