A typical 1 tbsp serving of sour cream contains 0.3 grams of protein (2.44 g per 100 g), which makes it only a minor source of protein. That covers roughly 1% of the 50 g reference Daily Value, so it adds toward your protein total for the day.
Only about 5% of the calories in sour cream come from protein, so it is more of an energy food than a protein food. It is worth eating for other reasons; the protein it adds to a day is incidental.
Among the 81 dairy foods in the database, sour cream ranks 81st by protein per serving, and 786th out of all 796 foods on the site. Set against sweet whey powder, another dairy food entry in the database, a serving carries about 0.7 g less protein (sweet whey powder has 1 g per 1 tbsp).
It is a complete protein - it supplies all nine essential amino acids in adequate amounts, so it can carry a meal's protein on its own. The serving above is measured by volume at 12 g. The per-100 g figure lets you compare it directly against any other food here, whatever its serving.
Source: USDA FoodData Central #171257 - "Cream, sour, cultured" (SR Legacy, published 4/1/2019). Values are the published reference figures for that record, not lab measurements for a specific brand or batch.
Quick answers
Sour cream protein FAQ
How much protein is in sour cream per 100 g?
Sour cream has 2.44 g of protein per 100 g. A typical 1 tbsp serving (12 g) provides 0.3 g.
Is sour cream a complete protein?
Yes. Sour cream is a complete protein - it supplies all nine essential amino acids in adequate amounts, so it can carry a meal's protein on its own.
How much of the Daily Value does a serving of sour cream cover?
A 1 tbsp serving of sour cream contains 0.3 g of protein, about 1% of the 50 g reference Daily Value.
Is sour cream a good source of protein?
Sour cream is only a minor source of protein, and about 5% of its calories come from protein, which makes it more of an energy food than a protein food. Set against sweet whey powder, another dairy food entry in the database, a serving carries about 0.7 g less protein (sweet whey powder has 1 g per 1 tbsp).