Yes, but this therapeutic magic is not chiefly due to its ingredients, as many people believe. The primary reason is because of the heat of the soup. The higher the temperature, the more fluid the mucus becomes and the more quickly it exits the respiratory tract. This is beneficial because mucus harbors cold-causing microbes. Chicken soup is not the only remedy. Another hot liquid such as a cup of tea would also serve the mucus-riding purpose.
If you do use chicken soup, make it from scratch. Commercial soups and bouillon cubes tend to be very salty, to the point where the soup will partially dehydrate you. That would be counterproductive because when you have a cold, your body needs an extra supply of water to combat and flush out the microbes and unwanted byproducts.