This study investigates the startup behavior and flow dynamics of a dual-evaporator loop heat pipe (DE-LHP) using neutron radiography. The DE-LHP is designed to overcome the challenges of efficiently managing multiple heat sources. Neutron radiography allows visualization of the liquid and vapor distributions, revealing phenomena like vapor backflow, liquid carryover, and heat leakage. Experiments were conducted with various heat load configurations, including balanced and unbalanced distributions, and different geometric orientations. The results show that at a balanced heat load (120 W total), the system reaches steady-state in 500 s with a thermal resistance of 0.14 °C/W while the highest thermal resistance of 0.64 °C/W was observed in the unequal heat load case of 56 W. The unbalanced heat load increases the thermal resistance and decreases the thermal efficiency due to uneven heat distribution and incomplete startup. Orientation studies show that the inclination of the DE-LHP reduces the liquid carryover and vapor backflow, improving the heat transfer efficiency. These findings provide valuable insights for optimizing the DE-LHP design and improving the thermal management system. © 2025 Elsevier Ltd