Leftover cooked ham should be refrigerated as soon as possible after serving. Do not allow the ham to set at room temperature for more than two hours.
Is it safe to eat ham that has been left out overnight?
It’s probably even safe to eat without cooking again, the refrigerator is likely only about 10 degrees colder, and that generally translates to accelerating rates of spoilage (mostly growth of pathogens) by a factor of 3-5 or so.
How long can ham go without being refrigerated?
Ham can sit out at room temperature for up to two hours according to the United States Department of Agriculture (USDA). This applies to all types of meat, including turkey, chicken, and sausage. After two hours, you should wrap it or put it in a sealed container in the refrigerator.