We present the results of a comprehensive investigation of electrical and thermal transport properties and their magnetic correlations in polycrystalline Bi substituted La_1-xSr_xCoO₃. The La_1-xSr_xCoO₃ system is well studied for the electronic, thermal and magnetic phase separation properties which is key to improve the thermoelectric efficiency of the material. The 5% substitution in La_1-xSr_xCoO₃ have peak of ZT at RT along with reversal of nature of charge carrier from p-n type around 290K make this system interesting for thermoelectric investigations. The choice of Bi substitution in this system has been made due to its high atomic weight and ability to increase S and hence in improvement of thermoelectric figure of merit keeping in mind. The effect of various spin state transitions due to the change of valence state of Co³⁺/Co⁴⁺ ions associated with the oxygen vacancies along with the effect of Bi-substitution on the structural, thermal transport, and electronic properties of LBSCO sample has been investigated thoroughly using x-ray diffraction, scanning electron microscopy and x-ray photoemission spectroscopy. More interestingly an anomalous feature observed in dielectric, resistivity and Hall measurements across the 50K that is associated with change of the nature of charge carrier, further verified with Seebeck measurements. At higher temperature the transport behaviour governs by small polaron hopping whereas at intermediate temperature range () the variable range hopping dominates the transport properties. Below 50K the role of the phonon drag effect for the phonon mediated charge carrier transport is confirmed by the thermal conductivity and Seebeck coefficient variation with temperature at different fields. The specific heat analysis helps to extract the electronic and phononic contribution in transport properties that shows the phononic contribution is much higher in the transport. The thermoelectric figure of merit has also been calculated and it shows the Bi-substitution helps to improve the PF as well as ZT significantly in comparison to existing cobaltite choices.