Hydrogels and 3D (bio)printing hold considerable promise for biomedical applications. Compared to conventional hydrogel fabrication strategies triggered by light, heat, or crosslinking agents, acoustic-assisted hydrogel fabrication and 3D (bio)printing offer unique advantages, including superior tissue penetration, high spatiotemporal controllability, and enhanced biosafety. This review systematically elucidates the significant potential and innovative mechanisms of ultrasound as a unique physical stimulus in these fields. We reviewed the fundamental principles of acoustic effects—cavitation, mechanical effect, and thermal effect—and their roles in hydrogel preparation. We then comprehensively discussed the multiple pathways for acoustic-assisted hydrogel fabrication, encompassing cavitation-triggered free-radical polymerization, mechanically/thermally induced polymerization, liposome-mediated and enzyme-catalyzed polymerization, self-assembly systems for polymerization, and homogenization effects in polymerization, highlighting their respective applications in biomedicine and other related fields. Subsequently, advances in the frontier field of acoustic-assisted 3D (bio)printing are reviewed in detail, ranging from the acoustic triggering of 3D printing with thermally curable/free-radical- polymerization inks to micrometer-scale 3D bioprinting using cell-laden bioinks. Finally, this review discusses current bottlenecks and future research prospects in the field of acoustic-assisted hydrogel fabrication and 3D (bio)printing.