Lyophilization, also known as freeze-drying, is a widely used method for stabilization, improvement of long-term storage stability, and simplification of the handling of drugs and/or carrier systems. Lyophilization is time- and energy-consuming; hence, optimized processes are required to avoid time loss and higher costs without compromising product stability. Since the last decade nonviral, synthetic carriers for gene delivery are of increasing interest. However, these systems suffer from poor physical stability in aqueous solution or suspension. Hence, to ensure long-term storage stability lyophilization of the gene carrier systems is favored. Though, lyophilized products retrieving original carrier size and transfection efficiency after reconstitution are mandatory. This chapter gives an overview of the basic steps and troubleshooting for successful lyophilization of synthetic gene carriers. Furthermore the required excipients and their mechanism of action are summarized.