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<i>β</i>-pinene is a monoterpene isolated from turpentine oil and numerous other plants’ essential oils, which has a broad spectrum of biological activities. In the current work, six novel <i>β</i>-pinene quaternary ammonium (<i>β</i>-PQA) salts were synthesized and evaluated in vitro for their antifungal, antibacterial and anticancer activities. The in vitro assay results revealed that compounds <b>4a</b> and <b>4b</b> presented remarkable antimicrobial activity against the tested fungi and bacteria. In particular, compound <b>4a</b> showed excellent activities against <i>F. oxysporum f.sp. niveum</i>, <i>P. nicotianae var.nicotianae</i>, <i>R. solani</i>, <i>D. pinea</i> and <i>Fusicoccumaesculi,</i> with EC₅₀ values of 4.50, 10.92, 9.45, 10.82 and 6.34 μg/mL, respectively. Moreover, compound <b>4a</b> showed the best antibacterial action against <i>E. coli</i>, <i>P. aeruginosa</i>, <i>S. aureus</i> and <i>B. subtilis</i>, with MIC at 2.5, 0.625, 1.25 and 1.25 μg/mL, respectively. The anticancer activity results demonstrated that compounds <b>4a</b>, <b>4b</b>, <b>4c</b> and <b>4f</b> exhibited remarkable activity against HCT-116 and MCF-7 cell lines, with IC₅₀ values ranged from 1.10 to 25.54 μM. Notably, the compound <b>4c</b> displayed the strongest cytotoxicity against HCT-116 and MCF-7 cell lines, with the IC₅₀ values of 1.10 and 2.46 μM, respectively. Furthermore, preliminary antimicrobial mechanistic studies revealed that compound <b>4a</b> might cause mycelium abnormalities of microbial, cell membrane permeability changes and inhibition of the activity of ATP. Altogether, these findings open interesting perspectives to the application of <i>β</i>-PQA salts as a novel leading structure for the development of effective antimicrobial and anticancer agents.