The olive leaf moth Palpita unionalis is one of the serious olive pests in Egypt and several countries. The objective of the current study was to evaluate the effects of methoxyfenozide, an ecdysteroid agonist, on survival, growth, development and metamorphosis of this pest. The newly moulted last instar (6^th) larvae were treated with six concentrations (100, 10.0, 1.00, 0.10, 0.01 and 0.001 ppm) via the fresh olive leaves, as food. The strongest acute toxicity (100% mortality) was exhibited against larvae at the highest concentration, but no mortality was observed at the lowest one. The developed pupae had been subjected to the toxic effect only at the higher three concentrations. Increasing adult mortality% was recorded at concentrations other than the highest or lowest one. LC₅₀ was calculated in 0.176 ppm. The somatic weight gain of larvae, growth rate, larval duration and developmental rate of larvae had been pronouncedly reduced. The pupal duration was non-significantly prolonged and the pupal developmental rate was slightly regressed. The successfully developed pupae suffered a desiccation action of methoxyfenozide. The metamorphosis program was impaired, since some larval-pupal intermediates had been produced. In addition, the pupal morphogenesis was deteriorated, since some pupal deformations had been produced after larval treatment only with 0.10 ppm.