Efficiency in recursive functions in C++ can be enhanced by preventing unnecessary calls. Tail call optimization is a key feature in some C++ compilers that allows the last recursive call in a function to execute without additional stack memory allocation, effectively transforming recursion into a loop and preventing stack overflow. Additionally, techniques like memoization and dynamic programming can be employed to store previously computed values, which is particularly useful in cases like calculating Fibonacci numbers, where repeated computations can be avoided. These strategies collectively improve the performance and reliability of recursive functions in C++.