Present research study was conducted for a period of 60 days to study the effects of different herbal seed powders - Celery (Apium graveolens), Fenugreek (Trigonella foenum-graecum) and Coriander (Coriandrum sativum) as feed additives on growth, haematology, digestive enzyme activity and stress levels of GIFT Tilapia (Oreochromis niloticus) fingerlings. Ten experimental diets were formulated, nine diets using Celery, Fenugreek and Coriander seed powder incorporated at 1.5%, 2% and 2.5% levels each and one control diet with no supplement. Protein content of the formulated diets ranged from 27.95 to 29.93% while as the lipid content ranged from 8.1 to 9.3%. The study design comprised of thirty PVC tanks (50L capacity) for triplicate experiment design with ten treatment groups per replicate. A total of three hundred fingerlings with ten fingerlings per tank were reared. At the commencement of the experiment, the fingerlings measured 3.48 ± 0.46 cm and weighed 3.41 ± 0.43 g on average. The fingerlings were reared in an indoor wet laboratory with filtered borewell water as freshwater source. Fingerlings were fed at the rate of 5% body weight daily in three rations. Growth and blood sampling was done fortnightly while as digestive enzyme activity and stress parameters were analysed at the end of the experiment. By the end of the experiment, growth performance in terms of Weight Gain, Specific Growth Rate (SGR), Relative Growth Rate (RGR), Protein Efficiency Ratio (PER), Feed Conversion Efficiency (FCE) and Feed Conversion Rate (FCR) was recorded. Treatment group fed with 2% Coriander seed powder supplemented diet showed the best results among all treatment groups. Highest Hepato-Somatic Indices (HSI) and Viscero-Somatic Indices (VSI) were observed in treatment group fed with 2.5% Fenugreek supplemented diet. Among the haematological indices, highest count of Red Blood Cells (RBC) was recorded in treatment group fed with 2.5% Coriander supplemented diet. Other parameters such as White Blood Cells (WBC), Haemoglobin (Hb), Haematocrit (Hct), Mean Corpuscular Haemoglobin (MCH) and Mean Corpuscular Haemoglobin Concentration (MCHC) values were recorded the maximum in fish treatment group fed with 2% Coriander supplemented diets. Maximum Mean Cell Volume (MCV) value was seen in Celery seed supplemented diets at 2% level. Highest blood protein content and glucose levels were observed in Coriander incorporated diets (1.5%) and control respectively. Further, among the digestive enzymes activity recorded, highest Trypsin activity was recorded in treatment group fed with Celery supplemented diet (2%), Lipase in Celery supplemented diet (1.5%) and Amylase in Fenugreek supplemented diet (2.5%). The oxidative enzymes were recorded for the estimation of stress. All the parameters (Catalase, Lipase Dehydrogenase (LDH), Malate Dehydrogenase (MDH), Sodium Oxide Dismutase (SOD) and Nitro-Blue Tetrazolium (NBT) showed the maximum activity in the group treated with Coriander seed supplemented diet at 2.5% level. By the end of the experiment trial, fingerlings fed with different seed incorporated diets showed a visible change in their body colouration. The results obtained from the present study suggest that supplementing fish diets with different herbal seeds reveal pronounced effects on different functional parameters such as growth, haematology, digestive and oxidative enzymes activity.