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This paper presents experimental evidence of homogeneous precipitation of the α-phase within the β matrix of a titanium alloy, and then accounts for this phase transformation by a new, non-classical mechanism involving compositional fluctuations, based on the pseudo-spinodal concept [1]. This mechanism involves local compositional fluctuations of small amplitude which, when of a certain magnitude, can favor thermodynamically certain regions of the β matrix to transform congruently to the α-phase but with compositions far from equilibrium. Subsequently, as measured experimentally using the tomographical atom probe, continuous diffusional partitioning between the parent β- and product α-phases during isothermal annealing drives their compositions towards equilibrium. For a given alloy composition, the decomposition mechanism is strongly temperature dependent, which would be expected for …