For several years, new plastic bottles made from opaque polyethylene terephtalate (PET) have been on the market. When their waste is mixed to those of recycled clear PET, the obtained material cannot be recycled anymore due to a loss of properties. Moreover, because of an important grade variety, the large number of additives used and poor homogeneity, the processing and recycling of opaque PET appears as a challenge. The way chosen to revalue this recycled opaque PET (r-OPET) is its microfibrillation in a recycled polypropylene (rPP) matrix. The effects of the concentration of r-OPET were studied by rheology, supported by scanning electron microscope images and related to the morphology of the mixture. It was demonstrated that (20/80) w r-OPET/rPP blend was the best ratio to favor microfibrillation, as it offers the appropriate amount of solid filler to obtain a sea-island morphology.