Ferromagnetic property of Co1.5Fe1.5O4 ferrite has been studied in a wide range of measurement temperature and magnetic field. Grain size effect on the ferromagnetic parameters has been examined by annealing the chemical routed sample at different temperatures up to 1150 0C. The evolution from hard to soft ferromagnetism of the material has been correlated with undergoing changes of crystal structure, grain morphology, crystalline anisotropy, and transformation of the ferromagnetic grains from single domain to multi-domain structure during annealing process. The present ferrite samples also showed some interesting low temperature features, e.g., blocking of ferromagnetic grains that started above 300 K and its control by varying magnetic field intensity, competition of the crystalline anisotropy between uniaxial and cubic character, large magnetic squareness and variable coercivity as the function of annealing temperature of the samples. The material seems to be technologically interesting for its high squareness value.