An entrainment flux model for freely bubbling gas-solid fluidized beds was described. The model was based on particle trajectories in the freeboard with consideration of interactions between the dense and lean phases. These interactions include a bubble eruption mechanism, namely, single and coalescence bubble eruptions, bubble induced gas puff velocity, and particle ejection mechanism. It was shown that the average particle velocity and entrainment profiles revealed a two-level decay trend. This could be attributed to different bubble eruption mechanisms; for single bubble eruptions where both the initial gas puff and ejected particle velocities were low, the first decay would form at lower freeboard height. The second decay trend at higher freeboard height would be formed by the higher gas puff and particle velocities due to the double-bubble coalescence eruption. However, the overall profile could be considered as an exponential decay with a slightly faster decay than Wen and Chen, AIChE J., 28 (1982) 117, suggested. A simple experimental set-up was used to confirm the two-level entrainment decay trend. The results obtained showed similar trends to the predictions from the model.