Origanum dubium Boiss. is an economically important wild oregano species that is intensely collected from the natural flora of Antalya, Turkey. This herb is used mainly to produce an essential oil due to its high yield and high carvacrol content. The aim of this study was to improve the biomass yield and essential oil and carvacrol content of O. dubium for industrial use. In preliminary studies, a basic population was established using seeds collected from wild plants and then trials of A and B clones were run. Dry biomass yield per A clone plant and essential oil content varied at 5.05-40.86 g and 5%-14%, respectively. Carvacrol was the main constituent in all samples and varied from 72.26% to 88.21%. Dry biomass yield per B clone plant was 21.64-95.52 g, dry leaf yield per plant was 14.80-48.77 g, essential oil content was 6%-9%, and carvacrol rate was 80.99%-88.46%. After evaluating the B clones, 10 clones were selected and they were planted in a plot with a randomized block design and three replications in Antalya in 2014. In this trial, clone 7 produced the highest biomass yields per plot (2874.33 g fresh and 1185.00 g dry) and the highest fresh (2379.67 g) and dry (795.33 g) leaf yields per plot. Essential oil content varied from 7.97% to 11.16%. Clone 137 had the best essential oil content (11.16%), followed by clone 7 (10.76%) and clone 119 (10.59%). Clone 7 appeared to be superior to the others in terms of agronomic features, followed by clone 119. Essential oil and carvacrol rates were 10.76% and 85.02% in clone 7 and 10.59% and 91.04% in clone 119, respectively. Consequently, clones 7 and 119 appeared to be superior to the others.