Yes, but not as long as when you also put ice in the cooler. The insulation of the cooler prevents the food from warming up as quickly as if it was left outside the cooler. How long food stays cool in a cooler without ice depends on how cold the food was initially, and also the temperature inside the cooler. In a cooler that was kept in the trunk of a car on a hot day food, even frozen food-will warm up much quicker.