The husbandry of chicken for meat generates high levels of gases, being a serious problem for the health of birds and workers as well as for the environment. The aim of the present study was to assess the effect of clinoptilolite as litter additive on the concentrations and emissions of ammonia (NH), nitrous oxide (NO), carbon dioxide (CO), and methane (CH) from a breeding hen house under Mediterranean climate conditions. Two similar breeding hen houses were selected, and one house was assigned as control whereas the other house was treated with clinoptilolite as a litter additive. Data were collected during the winter season, in two occasions, first between 26 November and 18 December 2017 and second from 1 to 20 February 2018. Results showed that the application of clinoptilolite on the litter of a breeding hen house reduces the NH and NO losses in 28 and 34%, respectively, but appears to have no effect on CO losses. In addition, the in-house CH concentrations were below the detection limits.