<p>The use of natural feed additives in poultry nutrition have been developed due to concerns over antibiotic resistance and consumer demand for healthier meat. Chia seeds (<i>Salvia hispanica</i> L.) are a nutrient-dense functional feed rich in fiber, protein, omega-3 fatty acids, and a range of micronutrients. However, their effects on broiler health and performance remain underexplored. This study assesses the impacts of chia seed on the body weight, nutritional composition, hemato-biochemical parameters and gut health in broiler chickens. Sixty hatched broilers were divided equally into five groups: commercial diet, hand-mixed diet, hand-mixed diet supplemented with 1%, 5%, and 10% chia seeds. The supplemented diet was provided from day 14 to 35. The 5% chia seed-supplemented group had the highest body weight and increased dry matter and protein content of breast meat. Chia seed supplementation at 5% and 10% concentrations increased red blood cells, hemoglobin, hematocrit and serum HDL (high-density lipoprotein) values while other hematological and serum biochemical parameters remained unchanged. Gut microbiota analysis showed no overall shift in viable bacterial count, but lactobacilli count was increased in the 5% chia seed group. The villi height, width and surface area were reduced, but crypt depth and mucosal thickness were increased. Our data indicated that 5% chia seed supplementation for two weeks enhances growth performances and gut health, while long-term consumption may have adverse effects. Further researches are required to optimize the dose and duration of chia seed supplementation in broiler diet. </p>