Luminescent materials with tunable emission wavelengths/colors hold great potential for smart response devices, data security, sensors, and so on. However, development of stimuli-responsive luminescent materials with traditional organic or inorganic luminophores remains challenging due to their lack of tunability. Herein, we report the tunable luminescence and ratiometric temperature sensing applications with a europium-organic cage (Eu₄L₄) featuring concentration-dependent hierarchical self-assembly behavior. Notably, white light emission was achieved by adjusting the equilibrium ratio between the red-emissive cage monomer and cyan-emissive cage aggregate. Taking advantage of the dual emissive nature of the system, ratiometric luminescent temperature sensing has also been achieved, exhibiting a sensitivity of 2.04% and linear correlation coefficient of 0.997 from 250 to 320 K.