Although the efficiency of organic solar cells (OSCs) has improved to a great extent and has gone beyond the value required to give competition to conventional solar cells, they are not stable enough. Degradation and poor stability are the biggest problems keeping OSCs away from commercialization. If OSCs are to replace silicon (Si) solar cells, prevention from decline in their performance with time is must. For prevention from degradation the understanding of degradation is of prime importance. The mechanisms controlling degradation in OSCs have been discussed in the previous chapter. Modification in chemical structures, oxidation of constituents, cross-linking of polymers and their chain scissions are some of the important factors causing degradation in OSCs. This chapter will focus on the methods suitable for prevention of degradation in OSCs. Before covering the methods adopted to prevent degradation in OSCs, let us first discuss the prevention of degradation in dye-sensitized solar cells (DSSCs) that will help us in understanding the prevention of degradation in OSCs.