Salmonella infections in poultry represent a significant public health and economic burden, particularly in regions where poultry serves as a major source of animal protein. Traditional control methods often rely on antibiotics, which contribute to antimicrobial resistance and raise consumer health concerns. This study developed a novel, sustainable strategy by integrating indigenous plant-based bacterial attenuation with immunotherapy using IgY antibodies. Specifically, garlic (Allium sativum) and onion (Allium cepa) extracts were employed to attenuate wild-type Salmonella serovars. These plant-derived agents exhibited strong antimicrobial properties, effectively inhibiting bacterial growth in vitro. The attenuated strains were then used to vaccinate chickens, which led to the induction of high levels of anti-Salmonella IgY antibodies, as confirmed by an enzyme-linked immunosorbent assay (ELISA). Functional assays revealed that the harvested IgY antibodies possessed robust agglutination activity, highlighting their potential role in passive immunisation strategies. Importantly, the vaccine was found to be both safe and immunogenic, with no adverse effects observed in the immunised birds. This dual approach—combining natural antimicrobial agents with immune-based protection—offers a cost-effective and environmentally friendly alternative to conventional methods. It holds particular promise for improving poultry health and food safety in the Caribbean, where locally available resources and affordable interventions are crucial. This strategy may also be applicable to broader global contexts, especially in low-resource agricultural settings.