Eucalyptus cultivation faces critical challenges regarding irrigation management and water quality in arid regions. This factorial study, conducted as a randomized complete block design with three replications in Dezful, southwestern Iran, evaluated the effects of three irrigation intervals (3, 6, and 9 days) and two water quality levels (raw wastewater and treated effluent) on growth, biomass yield, and essential oil content of Eucalyptus camaldulensis. Irrigation followed regional practices, totaling 9,061, 4,963, and 3,581 mm for respective intervals—substantially exceeding species' requirements due to sandy soil and arid conditions. Both irrigation interval and water quality significantly affected all parameters (p < 0.01). Increasing irrigation interval consistently reduced tree height, stem diameter, and biomass yields. The highest fresh wood (3.86 kg tree⁻¹), fresh leaf (6.50 kg tree⁻¹), dry wood (1.75 kg tree⁻¹), and dry leaf yields (3.49 kg tree⁻¹) were obtained under 3-day intervals with treated effluent. Raw wastewater reduced biomass yields by 16–74% compared to treated effluent. Notably, essential oil exhibited an opposing trend: the highest concentration (1.888%) occurred under 3-day intervals with raw wastewater, while the lowest (1.22%) under 9-day intervals with treated effluent. These findings demonstrate that while treated effluent at 3-day intervals maximizes biomass production, moderate stress from raw wastewater enhances essential oil concentration.