Abstract <p>This article presents the first systematic evaluation of the biological activities of phosphine oxide-functionalized cross-coupled triene derivatives—a class of compounds that uniquely integrate the electronic properties of organophosphorus motifs with the conformational dynamics of triethylenes. The study comprehensively assessed their antibacterial, insecticidal, and herbicidal characteristics against a panel of six phytopathogens, two weed species, and three arthropod pests. Results revealed distinct functional divergence. Notably, the compounds exhibited exceptional target-specific lethality against <i>Plutella xylostella</i> larvae, achieving 76% mortality at 500 ppm through dual exposure pathways—a performance that surpasses commercial broad-spectrum insecticides in environmental selectivity. While demonstrating limited antimicrobial efficacy and negligible phytotoxic effects, the compounds’ selective bioactivity profile highlights their potential as eco-friendly alternatives. Structure-activity relationship analysis identified critical molecular determinants: dimethyl-substituted acetylenes significantly enhanced bioactivity, while phenylacetylene derivatives showed certain pathogen-selective suppression against Rice stripe fungus. This work establishes phosphorus-triethylenes as a groundbreaking chemotype for targeted pest management, offering novel molecular blueprints for next-generation crop protection agents with minimized ecological impact.</p>