Copyright © 2016 John Wiley Sons, Ltd. A combination of Raman imaging with image analysis has been used to quantify the degree of mixing of cellulose nanocrystals (CNCs) in melt compounded high-density polyethylene (HDPE). Raman spectroscopy is shown to provide an accurate ‘fingerprint’ of the composition of the cross-sectional area of the end section of a formed composite. This information is then converted to a chemical image allowing spatial quantification of the mixing of CNCs in the HDPE. A degree of mixing between CNCs and HDPE is reported, with a strong tendency for the former to agglomerate with little dispersion. Freeze-dried CNCs show better mixing with HDPE and a lower tendency to agglomerate than spray-dried CNCs. This approach shows the potential to use Raman spectroscopy to quantify the degree of mixing of CNCs in a thermoplastic matrix. Copyright © 2016 John Wiley Sons, Ltd.