The present paper reports the pyrolysis behavior, kinetic, and thermodynamic parameters of paper mill sludge (PMS), which is a paper manufacturing residue and cannot be re-evaluated, at three heating rates (5, 10, and 20 degrees C min(-1)) under non-isothermal conditions. Ultimate and proximate analyses of the paper mill sludge were carried out. Kinetic and thermodynamic parameters were calculated using four model-free methods; Flynn-Wall Ozawa (FWO), Friedman, Kissinger-Akahira-Sunose (KAS), and distributed activation energy model (DAEM). High R-2 values revealed that all models are compatible with TGA data. The activation energy calculated (101.01 kJ mol(-1)) from FWO was higher than the other three methods. Pre-exponential factor values ranged from 0.56 x 10(3) and 14.55 x 10(3) s(-1) for all methods. Kinetic and thermodynamic findings will be beneficial in terms of the process design of PMS pyrolysis.