The present study aimed to investigate the potential application of chitosan for controlling green mold disease of orange fruits (“Baladi” sweet orange fruits) caused by Penicillium digitatum under in vitro and in vivo conditions (during storage conditions). The effect of chitosan under different concentrations (0.01, 0.025, 0.05, 0.125, 0.25, 0.5, 1 and 2) % v/v was evaluated against P. digitatum (in vitro). The reported data indicated that conc. 0.25, 0.5, 1 and 2% v/v of chitosan showed the highest inhibitory effect against the target pathogen. The in vivo experiments (under artificial infection), showed that the disease severity was significantly reduced in chitosan treated fruits at conc. (0.25, 0.5 and 1% v/v) compared with control. Moreover, it was noticed that chitosan solution at 1% conc. was the best conc. in reducing the percentage of disease severity, followed by 0.5% v/v. The effect of chitosan at (0.25, 0.5 and 1% v/v) conc. was also studied on some physical and chemical characteristics at 4 °C during two successive seasons. Interestingly, chitosan at 1% followed by 0.5% decreased fruits decay percentage, 0.5% and 1% significantly decreased fruits weight loss percentage, increased total soluble solids (TSS) and V.C content in fruits. The uses of edible coating of chitosan solution (0.5 and 1%) were more effective to preserve high quality of “Baladi” sweet orange during storage 4 °C for 8 weeks with good chemical and physical qualities as well as chitosan could be successfully used to inhibit the decay fungi compared with uncoated samples.