In tablet manufacturing, a lubricant is added in a tumbling mixer prior to compression to ensure that the tablet is ejected smoothly without sticking or breakage. Control and monitoring of this process is critical as process parameters can negatively affect final tablet properties. Inline monitoring methods including passive vibration measurements could be implemented to improve process efficiency. This method is non-invasive, non-destructive, and has a reduced cost compared to other monitoring techniques. Using an accelerometer affixed to the lid of a V-blender, magnesium stearate was added to glass beads and granule formulations and monitored to determine the effect of lubricant concentration, particle size, and particle size distribution on vibration measurements. Mixing end-points were identified and changes in mixing profiles were reflected in signal amplitude and variation. This research indicates that passive vibration measurements have the potential to be used as a real-time inline monitoring method for lubricant addition. (C) 2020 Elsevier B.V. All rights reserved.