A three-phase study was conducted to investigate the effects of individual components in a vitamin E formulation (CF-120) on off-odor release, melt flow index, and yellowness index of high-density polyethylene (HDPE) resin pellets. CF-120 consists of vitamin E, glycerol, polyethylene glycol-400 (PEG-400), and glyceryl monocaprylate/caprate (GMC). The resin pellets were extruded from HDPE resin powder using a laboratory-scale single-screw extruder. Off-odor release from the resin pellets was evaluated using a sensory panel and gas chromatography/mass spectrometry (GC/MS) analysis. A Phase I (preliminary experiment) study showed that GMC greatly contributed to off-odor and melt flow index (MFI) reduction; vitamin E greatly contributed to yellow color formation. A Phase II (factorial experiment) study confirmed that GMC was the major off-odor contributor. A Phase III (response surface experiment) study showed that yellowness index and odor score reasonably correlated to vitamin E and GMC concentrations. In contrast, MFI and nonanal concentration had no correlation with vitamin E and GMC concentrations. The results are useful for designing a better vitamin E formulation for reducing the off-odor, without significantly enhancing yellow color formation.