Applying vibrations on heat sinks can induce recirculation zones in the flow field, disrupting the developed thermal boundary layer. This paper demonstrates the fin spacing effect on the vibration-assisted heat transfer of the heat sink. Thermal performance is investigated over a range of 0-12 Hz vibrational frequencies and fin spacing of 0.008 - 0.014 m. The enhancement of the Nusselt number is insignificant up to the threshold frequency (6 Hz). This threshold frequency is found to be independent of fin spacing. Further increase in vibration frequency leads to higher enhancement in Nusselt value at every fin spacing. However, the vibration effect on the Nusselt number became more prominent at lower fin spacing. In this study, the enhancement of the Nusselt value is up to 8 at a fin spacing of 0.008 m and a vibrational frequency of 12 Hz. © 2023 Institute of Physics Publishing. All rights reserved.