Despite extensive research on the bed particle layer formation and characteristics of ilmenite bed particles in fluidized bed combustion and gasification of woody biomass (characterized by high Ca and K content), a significant knowledge gap exists when P-rich fuels are used. Chicken litter, as a P-rich biomass, presents a promising alternative biomass for energy conversion processes. Therefore, this study aims to investigate the bed particle layer formation and characteristics of ilmenite bed particles during fluidized bed combustion of chicken litter. The bed particle layer formation process and characteristics for ilmenite bed particles utilized in a 5 kWth bubbling fluidized bed combustion of chicken litter were studied in this work. Bed samples were taken after 4, 8, 12, and 16 h from the start-up and were analyzed via SEM/EDS. The findings highlighted that the initial stage of bed particle layer formation is similar to what was observed in fluidized bed combustion of woody biomass and is driven by the reaction of fuel-derived Ca-rich particles with the bed particle, leading to the formation of the inner layer. As time progresses, the deposition of fuel-derived bed ash, containing mainly Ca, P, Mg, and K, forms an outer layer that uniformly covers the entire bed particle surface, irrespective of the bed particle’s surface morphologies. Additionally, the outward migration of Fe from ilmenite bed particles is significantly constrained when utilizing chicken litter, a Ca- and P-rich fuel, due to the formation of a bed particle layer that uniformly covers the bed particle surface.