<p>The red bird mite (Dermanyssus gallinae) is an ectoparasite that affects the health of laying hens. Essential oils act as control agents against these mites. The present study evaluated the acaricidal effect of the essential oil of Thymus vulgaris against D. gallinae from laying birds in Tinjaca (Boyacá - Colombia). The essential oil of T. vulgaris in concentrations of 0.05, 0.1, 0.15, 0.20 and 0.25 mg / cm2 was evaluated through contact bioassays under laboratory conditions. A 100% mortality of&nbsp;&nbsp; D. gallinae was obtained with the essential oil of T. vulgaris in concentrations of 0.05 and 0.25 mg / cm2, after 35 minutes of contact. The LC50 was 0.073 mg / cm2 and the TL50 was 13 minutes. The use of thyme essential oil can be suggested as an alternative for the control of the red mite of birds in poultry farms.</p>