The parasitism and host feeding behavior of Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) females on Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) fourth instars that have infested tomato (Lycopersicon esculentum Miller) leaflets are described and quantified. Females took approximately 31.14±4.39 min to search for their first suitable host. The recognition and handling times for oviposition were 2.66±0.18 and 4.26±0.39 min, respectively. T. triozae parasitized 4.66±0.61 nymphs in a period of 6 h. The parasitoid explored and probed its host by walking along the margins of its body while antennating and repeatedly introducing the ovipositor beneath the nymph. The handling times before and during host feeding were 8.42±0.67 and 8.29±0.60 min, respectively. T. triozae females consumed 1.00±0.00 B. cockerelli nymph after parasitizing 3.3±0.48 nymphs. EPA—a refined soybean oil—imidacloprid, and abamectin caused between ∼70 and 100% T. triozae adult mortality after a 48-h contact treatment with fresh pesticide residue and a 47–91% decrease (abamectin > imidacloprid > EPA) in adult emergence when parasitized B. cockerelli fourth instars were directly sprayed. These data suggest that the use of these insecticides in combination with T. triozae in integrated pest management programs should be carefully evaluated.