The application of the generalized variational principles to controlled thermonuclear reactor (CTR) neutronics studies has been demonstrated using the neutronics analysis for a laser-driven molybdenum-structured CTR blanket. The variational functionals could be derived and proved identical mathematically with the well-known perturbation theory. The variational and perturbational functionals are alternatively useful in a fixed adjoint source and a fixed system perturbation problem. The neutronics calculational results using these techniques show the accuracy, range of applicability, and extremum property of their applications.