Abstract Olive mill wastewater (OMW) is a problematic by-product in Mediterranean countries. Despite this, it is a raw material that is an unfailing source of bioactive molecules. A hydroxytyrosol-rich preparation (HRP) (49.6% weight:dry weight) was extracted from fresh OMW using a hydrolysis and post-hydrolysis purification process. The field efficacy of HRP as a spray treatment (2500 l ha −1 ) against olive psyllid, Euphyllura olivina (Hemiptera: Psyllidae), was evaluated in 2008 and 2009 in a drip-irrigated olive orchard. The HRP showed strong insecticidal activity against E . olivina at a concentration of 2 g l −1 hydroxytyrosol. Application of HRP resulted in 41.1 and 72.1% control of nymphs and adults, respectively. However, HRP application did not reduce egg hatch. Neither phytotoxicity nor toxicity to auxiliary-fauna was recorded with concentrations of 1.25 g l −1 or 2 g l −1 HRP. But, the 2.5 g l −1 concentration was slightly phytotoxic, especially at the E and F floral phenological stages of the grapes. HRP offers a natural and effective extract for control of olive psyllid and opens a new opportunity for the reuse of OMW.