<p>Artificial lighting, particularly light-emitting diodes (LEDs), is widely used in controlled-environment agriculture (CEA) to enhance crop productivity. However, the impacts of LEDs on multitrophic interactions remain poorly understood. This study assessed how spectral photoperiod extension modulates top-down effects (predator effects on pest density, pest-related damage to plants, and plant defense-related gene expression) and bottom-up effects (plant morphology, light assimilation, defense and growth hormone-related gene expression) in a tri-trophic system involving a plant, greenhouse cucumber (<i>Cucumis sativus</i>), a pest insect, the western flower thrips (<i>Frankliniella occidentalis</i>), and a predator used for biological control, the minute pirate bug (<i>Orius insidiosus</i>). Plants were exposed for two weeks to a 12-h artificial sunlight, with or without an 8-h extension of blue, blue–red, or blue–green–red LEDs. <i>Orius insidiosus</i> reduced thrips populations by 96 ± 9%, regardless of light treatment, and decreased foliar damage due to thrips by 46% on average. <i>Orius insidiosus</i> produced offspring under all lighting conditions, although total numbers of the predator were lower under blue–green–red lighting. Pest densities remained similar across all light treatments, suggesting that light supplementation did not benefit <i>F. occidentalis</i>. Blue and blue–red spectra improved plant light assimilation, and photoperiod extension generally increased dry biomass (9 ± 6%). Defense-related phytohormones were only marginally affected. Surprisingly, some jasmonic acid pathway-related genes were upregulated in the presence of predators, suggesting additional plant-mediated effects. Our results underscore the potential of <i>O. insidiosus</i> to provide biological pest control services under artificial lighting regimes already used in crop production.</p>