We explore, in detail, the remarkable influence of spin-state transition – low (S = 1/2) to high spin (S = 5/2) – on crystallographic, thermal, electrical, and mechanical properties in Ba_0.5Sr_0.5Co_0.8Fe_0.2O_{3−ð�›¿} ceramic. The low to high spin transition takes place at T^∗ ~ 600 K with a rather broad transition zone of nearly 200 K. We find that the electrical resistivity, mechanical stiffness and toughness, thermal expansion coefficient, and the crystallographic structure exhibit clear anomalous features around T^∗. The transition, however, appears to be isostructural  Pð�‘š3^-ð�‘š → Pð�‘š3^-ð�‘š (cubic → cubic). Significant influence of spin-state transition on a variety of properties could have serious implications for several applications ranging from magnetic sensors to electrocatalysts to ion separation membranes.