According to Atkins' official site, a number of cheeses are optimal for the diet. By the time you reach Phase 2, almost all cheeses are acceptable. However, a number of them are also acceptable during the diet's first phase. This is the phase where carbs are restricted the most, to no more than 20g of net carbs a day. The cheeses allowed in Phase 1 have the lowest amount of carbs.
Cheddar is the best cheese for Atkins because it contains zero grams of net carbs per 1-ounce serving. If you don't have access to labels to compare different cheeses, stick to aged cheeses. According to Astro Nutrition, these, along with full-fat, firm cheeses, are overall the best options.
One Gram or Less
A number of cheeses contain less than a gram of net carbs per serving. For example, a tablespoon of parmesan cheese contains 0.2g of net carbs. Sheep and goat cheeses are also very low in carbs, at 0.3g of net carbs per 1-ounce serving. Other options under 1g include blue cheeses, Gouda, mozzarella and cream cheese.
One Gram or More
The only two cheeses that are over 1g of carbs per serving but are still acceptable during Phase 1 are feta and Swiss cheese. Feta cheese contains 1.2g of net carbs per serving, and Swiss contains 1g.