This study explored the potential of osmotic dehydration (OD) and ultrasound-assisted osmotic dehydration (USOD) as pretreatment strategies for semi-dried red-fleshed dragon fruit (RFDF) by evaluating their impact on drying kinetics, quality attributes, and sensory preference. Erythritol and sucrose solutions of 30°Brix and 50°Brix were evaluated as osmotic agents, demonstrating distinct effects on process efficiency and product quality. The application of USOD significantly enhanced mass transfer, where a 10-min treatment yielded water loss comparable to 120 min of conventional OD. These modifications translated into accelerated drying kinetics, specifically in reducing the predicted drying time from 12.62 h (control) to 9.92 h (USOD with 30°Brix erythritol, USOD_30E), representing a 21.4% increase in efficiency. While a high sucrose concentration (50°Brix) improved initial water loss, it led to structural modifications that increased internal resistance, resulting in longer drying duration (12.38 h). Physicochemical analysis revealed that USOD_30E best preserved functional attributes, maintaining betacyanin content (12.93 mg/100 g), total phenolic content (47.09 mg gallic acid equivalent/100 g), and antioxidant capacity nearly identical to the control. Microstructural stability of this sample was significantly improved, characterized by reduced shrinkage (from 28.28% to 16.84%) and higher color vibrancy, with the total color difference value of 7.19 indicating a distinct visual enhancement. Sensory evaluation supported these findings, revealing that the USOD_30E obtained high acceptability in terms of color, texture, and taste with average scores of >7.0 over 9.0. The findings proved that the combination of ultrasound and erythritol could be effectively employed to produce high-value semi-dried dragon fruit rich in bioactive compounds while maintaining its sensory quality.