LiNi0.33Mn0.33Co0.33O2 (NMC) is a promising substitute for LiCoO2 because of its good thermal stability and high energy density. In this work, the lithium concentration distributions in an NMC cathode using neutron computed radiography technique at Oak Ridge National Laboratory’s High Flux Isotope Reactor (HFIR) CG-1D Cold Neutron Imaging Facility. Samples with four different state of charge (SOC) were prepared for neutron imaging: 70% SOC, 100% SOC, 105% SOC, and 110% SOC. The neutron tomographic reconstruction of NMC cathode reveals the information of electrochemical transport and spatial Li distribution inside the cathode. The experimental results were explained by a diffusion numerical model which maps the Li concentration evolution during the electrochemical reactions. The study demonstrates that neutron imaging technique can be a very powerful tool to understand the lithium concentrations and evaluate its state of conditions, thus providing information for design of safe lithium ion batteries and estimating their lives.