Abstract: The haematological and growth parameters of the African mud catfish, Clarias gariepinus fed with imported pelleted feeds (Durantee) and raised separately in In-Door Concrete (IDC) and out-door Earthen (ERT) ponds for a period of 12 weeks at the fish farm of the Department of Environmental Biology and Fisheries, Adekunle Ajasin University, Akungba Akoko, Nigeria were assessed in this study. The water quality of the two rearing systems was also studied on a weekly basis. Blood samples were collected from the fish samples by puncturing the caudal peduncle with heparinized plastic syringe. The values of the haematological parameters were measured using standardized and approved methods. The water parameters studied in IDC showed that the temperature (28.543±0.20°C) dissolved oxygen (0.734±0.38 mg L^-1) salinity (0.223±0.03%) conductivity (0.002±0.00 MΩ cm^-1) total dissolved solids (275.750±31.26 ppm) and nitrate (2.520±1.45 ppm) statistically differed (p<0.05) to 27.321±0.71°C, 7.118±0.46 mg L^-1, 0.099±0.00%, 0.004±0.00 MΩ cm^-1, 102.580±2.53 and 0.000±0.00 ppm obtained, respectively in ERT. However, the values of pH (7.062±0.13) nitrite (0.500±0.26 ppm) and total hardness (40.000±6.96 ppm) in IDC were not significantly different (p>0.05) to the values 7.128±0.14, 0.000±0.00 ppm and 39.000±0.00 ppm obtained, respectively in ERT. The packed cell volume (34.600±3.297%) red blood cell (3.430±0.424x10⁹ g dL^-1) lymphocyte (55.900±5.010%) haemoglobin (11.155±1.213 g dL^-1) thrombocyte (12.700±1.989%) white blood cell (121700.000±34012.759x10⁹ g dL^-1) mean corpuscular volume (105.852±5.544 fl) mean corpuscular haemoglobin (33.800±1.874 pg) and mean corpuscular haemoglobin concentration (32.035±1.100 g dL^-1) of the catfish in IDC were not statistically different (p>0.05) compared to 28.400±2.956%, 2.670±0.394x10⁹ g dL^-1, 51.200±3.723%, 8.640±0.953 g dL^-1, 15.400±2.522%, 197300.000±37057.028x10⁹ g dL^-1) 112.935±7.594 fl, 34.423±2.578 pg and 30.394±0.780 g dL^-1 obtained, respectively in fish raised in ERT but the values obtained for neutrophils (31.400±6.462% in ICD) and (30.400±4.507% in ERT) showed significant variations (p<0.05). The study also showed that the fish population in IDC attained statistically higher average weight (0.58 kg) compared to the fish in ERT (0.44 kg). It is recommended that closed fish culture should be encouraged in order to reduce pressure on land and deforestation usually associated with earthen pond construction.