The mechanical properties of mechanically recycled polyethylene (rPE) were studiedin relation to the composition of the feedstock. This composition varied in six stepsfrom only bottle bodies from a single type of high-density polyethylene (HDPE) tothe complete composition of an industrially sorted polyethylene (PE) product,including other packaging components, other PE-based packages, sorting faults andresidual waste. The rPE with the highest impact resistance was made from the single-grade bottle bodies. The addition of bodies made from other types of PE alreadyreduced the impact resistance with 11%. All the other stepwise additions ofpackaging components and faultily sorted objects caused the impact resistance todecrease further. Conversely, the elongation at break grew with the stepwiseaddition of these packaging components and faultily sorted objects. From the usedmethods, the best analysis method to accurately determine the polymericcomposition of the rPE was found to be near-infrared-assisted flake analysis. Thismethod can not only be used to determine the polymeric composition, but due to thestrong correlation with the impact resistance, it is also a valuable indicator for theexpected mechanical properties of rPE.