<p>This study explores the vibration isolation performance of acoustic blackhole (ABH) beams filled with viscous fluids. ABH structures employ a power-law tapering in thickness to decelerate flexural wave propagation, effectively concentrating and trapping vibrational energy. Incorporating a viscous fluid within the ABH structure further enhances damping performance through viscous effects and fluid-structure interactions. Theoretical models are developed to predict transfer functions and reflection coefficients, with predictions validated through experimental testing. Results demonstrate that ABH beams substantially reduce resonance peaks and vibration amplitudes compared to uniform beams, particularly in the mid-to-high frequency range. Furthermore, the presence of viscous fluid enhances the damping effects, resulting in minimal reflection coefficients and improved energy dissipation. Experimental results confirm a strong agreement with theoretical predictions, emphasizing the effectiveness of integrating viscous fluids with ABH structures for broadband vibration control. These insights support the advancement of lightweight and highly efficient vibration isolation solutions in aerospace, automotive, and structural engineering applications.</p>