The future of the bivalve mollusk production sector worldwide is still challenged by emergence and propagation of new diseases, mainly vibriosis, and the conventional methods that have been used to eradicate pathogens from hatcheries, such as antibiotics and chemotherapies have shown collateral effects. In order to reduce the use of conventional methods, homeopathy for aquaculture emerges as a novel solution to strengthen marine organism’s defense against diseases. This study evaluated the effect of five homeopathic treatments on the immunomodulatory response and general condition index of Argopecten ventricosus juveniles, used as model organisms due to their susceptibility to vibriosis compared to other commercial bivalves. The experimental design included three replicates of five homeopathic treatments at decimal (D) or centesimal (C) dynamization (T1: ViA 1D + ViP 1D, T2: ViA 7C + ViP 7C, T3: AcF 1D + MsS 1D, T4: PhA 7C + SiT 7C and T5: ViT 31C) and three control groups (C1: Dynamized Ethanol (1C), C2: Diluted Ethanol (1:99) and C3: No medication). The maximum immunomodulatory response was attributed to treatments T1 and T2 with the highest increase in hemocyte count, catalase activity in mantle and superoxide dismutase activity in gills, followed by treatments T3 and T5. Treatment T4 did not show a definite effect on an immune response but increased energetic reserves in the mantle, muscle and the digestive gland, important storage tissues in mollusk bivalves. This study has demonstrated that some homeopathic treatments can activate an immunomodulatory response and improve the general condition index in A. ventricosus.