Organic aquaculture aims to provide sustainable aquatic products, and utilizing innovative aquafeeds with less fish meal is crucial. This study evaluated the impact of a cost‐effective and environmentally friendly diet (51% replacement with plant/animal protein sources like fermented soy, pea, krill, squid, and yeast meals) on gilthead seabream (Sparus aurata) growth, health, and welfare using a multiparametric approach (growth, swimming activity, blood health, and welfare indicators). The innovative diet showed no adverse effects on growth performance and survival. Hematological and biochemical blood indicators demonstrated minimal alterations, with only lactate levels increasing, suggesting no compromise in overall welfare. Immune features indicated a potentially stronger innate immune response in fish fed the innovative diet, as shown by higher levels of total proteins, alpha 1, and beta 1. Finally, a slight difference was observed in swimming activity between diets, but primarily occurred at the end of the day. A comprehensive multiparametric analysis and multi‐criteria decision analysis indicated better global welfare and health status with the innovative diet compared to the control. While the innovative diet showed promising results for gilthead seabream organic aquaculture, further long‐term investigations are necessary to explore the underlying causes of the observed immune parameter changes.