Current knowledge about the optimal energy and nutrient supply for common marmoset monkeys (Callithrix jacchus) is scarce, and more information is needed for establishing the underlying nutritional concepts for facilitating longevity of this species as laboratory animals for biomedical research. Two feeding experiments were conducted to yield fundamental data about feed acceptance, real feed intake, and feed preferences under laboratory conditions. Newly developed feeding concepts for marmoset monkeys were also examined in preliminary investigations to compare the outcomes with those of a commercial pelletized mixed feed. The first experiments showed preferences for main protein sources in the diets studied, specifically that plant proteins are more accepted than fish meal or egg protein as the main protein source. Several aroma supplements did not modify the acceptance and feed intake markedly. The newly developed feeding concept yielded promising preliminary data for long-term studies of energy and nutrient supply under laboratory conditions. However, studies of the fundamental requirements are still needed.