The low frequency electromechanical oscillations (LFEOs) in electric power system are because of weaker inter-ties, uncertainties, various faults and disturbances. These LFEOs (0.2-3 Hz.) are less in magnitude and are responsible for lower power transfer, increased losses and also threaten the stability of power system. An adaptive interval type-2 fuzzy sliding mode controlled power system stabilizer (AIT2FSMC-PSS) is presented to neutralize the LFEOs and enhance stability under uncertainties and external disturbances. The AIT2FSMC is a hybridization of type-2 fuzzy logic system (T2FLS) with conventional SMC to lower the chattering effect, enhance the robustness of reaching phase and improve system’s performance. Here, T2FLS is used for estimating the unknown functions of SMC. A robust sliding surface is presented to keep the system in the desired plane and remain stable under disturbance conditions. A modified control law is proposed for selecting the control parameters and Lyapunov synthesis is used to make the error asymptotically converging to zero. The effectiveness of the AIT2FSMC-PSS is accessed in single and multimachine power systems subjected to various uncertainties and disturbances. Again, comparison of performance indices (PIs), Eigen values, damping ratios, oscillating frequencies, integral time absolute error (ITAE), figure of demerit (FD) and frequency domain plots like Bode, root locus and Nyquist plots are also analyzed to access the efficacy of the proposed stabilizer. The simulated responses, comparative study and frequency plots conform the supremacy of the proposed AIT2FSMC-PSS in suppressing the LFEOs with lesser settling characteristics, offer stable performance and assures transient stability of power system as compared to other stabilizers.