Pyridinium salts are valuable building blocks, which have been widely applied in various organic transformations during the past few decades. In particular, N-functionalized pyridinium salts have been explored as convenient radical precursors, which would go through reductive single-electron transfer. As a result, the chemistry of such pyridinium compounds for generating carbon-, nitrogen-, and oxygen-centered radicals has been witnessed, and a remarkable progress has been achieved, making it a hot topic over the last five years. This Review describes recent advances in the area of pyridinium salts as radical precursors, concerning the development of radical reactions involving pyridinium salts in organic synthesis.