Esparto is a gramineous plant that has multiple applications in today's industry. Several cases of hypersensitivity pneumonitis (HP) caused by esparto inhalation have been reported, but only one case of asthma caused by Aspergillus fumigatus contaminating esparto has been communicated. We report a case of asthma induced by esparto inhalation in a 58-year-old man, who is a building industry worker, with subclinical sensitization to grass pollen. The relation between clinical symptoms and work activities was supported by peak expiratory flow (PEF) monitorization; PEF values decreased by 20% the days he handled esparto. Prick test with esparto was positive. Immunoblot analysis revealed several allergens in the esparto extract, some of them present in Lolium and A. fumigatus extracts. IgE immunoblot inhibition revealed a complete inhibition of lolium and A. fumigatus IgE reactive bands by esparto proteins. The patient then avoided the exposure to esparto at work and has remained asymptomatic for the last 2 years. In conclusion, this is a case of occupational asthma caused by esparto dust mediated by IgE antibodies. Proteins of A. fumigatus as well as proteins from this gramineous plant, which cross-reacted with esparto allergens, were responsible for the disease.