In this study, the shelf life of fresh-cut iceberg lettuce (Lactuca sativa L.) was evaluated. Lettuce samples were washed with disinfectant agents and sodium hypochlorite and then soaked in an ascorbic acid solution. Next, samples were stored in packaging films containing three levels (1% and 3% and 0% as a control film) of nano-bentonite particles (NBPs) as a filler in a modified atmosphere for 12 days at 4 °C. Various physicochemical parameters such as color, texture, pH, titratable acidity, dehydration, moisture, dry matter, chlorophyll content, microbial quality, and sensory properties were investigated. Results indicated that nano-packaging had a significant ability to maintain the sensory physicochemical properties of lettuce at the fifth (1% nano-composite film) and ninth (3% nano-composite film) days of storage when compared to the control films. The greatest growths of molds and yeasts were observed in the control films, which demonstrates the effectiveness of the application of bentonite nanoparticle fillers.