The aim of this study was to investigate the effects of different packaging systems on the shelf life of refrigerated ground beef. The ground beef samples were packaged as follows: AA (100% ambient air), 90O:10CO (90% O and 10% CO), 80O:20CO (80% O and 20% CO), 70O:30CO (70% O and 30% CO), 60O:40CO (60% O and 40% CO), 50O:50CO (50% O and 50% CO), 100O (100% O), and VP (vacuum packaging). All treatments were analyzed daily for O and CO levels, pH, filtration time, total volatile basic nitrogen (TVB-N), aerobic mesophilic heterotrophic bacteria (AMHB), and aerobic psychrotrophic heterotrophic bacteria (APHB) over 20 days at 2 °C. All MAP systems had a decrease of O and an increase of CO levels during storage period ( < 0.05). Overall, the MAP systems were similarly able to decrease the pH and retard the increase of TVB-N and filtration time over the storage period ( > 0.05). Moreover, the MAP systems increased the lag phase and/or the generation time of both AMHB and APHB, extending the shelf life by 3 (90O:10CO), 4 (70O:30CO and 100O), and 5 days (80O:20CO, 60O:40CO, 50O:50CO and VP). All MAP systems were equally effective in retarding physicochemical degradation; however, 80O:20CO, 60O:40CO, 50O:50CO and VP were the most effective in impairing bacterial growth and extending the shelf life of ground beef stored under refrigeration.