Pineapple peel is recognized as a widely available lignocellulosic biomass that offers considerable potential for upgrading into valuable products. The removal of lignin, or delignification, is vital to improving cellulose accessibility for further biomass conversion. Recently, deep eutectic solvents (DES) have demonstrated effectiveness as green delignification agents. This environmentally sustainable method aligns well with contemporary initiatives to manage agricultural waste more responsibly while encouraging the adoption of cleaner processing protocols. This study investigates the delignification capability of DES on pineapple peel and performs structural characterization of the altered biomass. The study varied the hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) types and their molar ratios, using choline chloride (ChCl) and betaine as HBAs, and lactic acid (LA) and glycerol as HBDs. The molar ratios tested ranged from 1:2 to 1:9. According to Chesson–Datta analysis, the application of ChCl:LA at a molar ratio of 1:9 for one hour effected a 95% reduction in lignin and increased cellulose content to 65.54%. FTIR analysis confirmed the disappearance of lignin-specific peaks, SEM observations showed a more porous fiber morphology, and XRD measurements indicated a significant rise in crystallinity from 29.18% to 41.11%.