<p>A novel attitude determination and control system for inertia-morphing spacecraft is presented. This system makes use of the natural Dzhanibekov (DZH) effect (periodic 180-degree flipping motion that occurs in rigid bodies when spinning about their intermediate axis of inertia) to enhance the system’s performance. This investigation has two purposes. First, it is demonstrated that the DZH effect can be controlled (enabled/disabled) through an inertia-morphing actuator composed of two moving masses. Second, it is proposed that the combination of the DZH effect with reaction wheels and a Proportional-Integral-Derivative (PID) controller can save energy and time of use of the reaction wheels during the attitude maneuvers. An advanced attitude control algorithm computes the optimized values of the reaction wheels’ PID gains and the time at which they are activated along the DZH flipping motion. From this optimal activation time, the reaction wheels are used to point the spacecraft to the target attitude. A comprehensive dynamic simulator containing the coupled equations of motion of the spacecraft, the reaction wheels, the PID, and the moving masses is used to accomplish these two goals. The numerical investigation shows that nearly 80% of the maneuvers are about 50% more energy efficient as compared to only using reaction wheels when minimizing energy consumption. About 50% of the maneuvers present moderate values of time gains (<InlineEquation ID="IEq1"> <EquationSource Format="MATHML"><math> <mo>∼</mo> <mn>20</mn> </math></EquationSource> <EquationSource Format="TEX">$\sim 20$</EquationSource> </InlineEquation>%) when minimizing the time of use of the reaction wheels. This work constitutes a theoretical verification of a system and methods later implemented in a spacecraft prototype and tested in a parabolic flight campaign organized by the European Space Agency.</p>