Hermetia illucens (edible insect) larvae protein, and hydrolysates were prepared using three pretreatment modes (conventional, fixed-frequency ultrasonic, and sweep-frequency). Protein subunit scores, microstructure, antioxidative activity, and techno-functional property of the respective isolates and hydrolysates were investigated. Alkaline protease hydrolysis significantly enhanced protein solubility, but impaired the emulsifying property and foaming stability. Isolates and hydrolysates treated by ultrasound exhibited highest antioxidative effect, and showed excellent solubility and foam expansion over wide (2–12) pH, likened the conventional. Ultrasonic, particularly sweep-frequency, treated hydrolysates overall showed superior solubility, foam, and antioxidative (ABTS, Superoxide scavenging, and Ferric-reducing) capacity than the remaining modes and isolates (p < 0.05). Treatment type influenced microstructure, functional attributes and antioxidative capacity of hydrolysates and isolates. Thus, functional/antioxidative property could be improved or modified for different food applications based on elected treatment. H. illucens isolate and hydrolysate preparations thereof could suitably be used in development of novel food formulations.