More than a dozen viruses can infect tomatoes. Tomatoes can suffer from viral infections, which can significantly reduce productivity and fruit quality. The most common viruses are tomato mosaic virus (ToMV) and tobacco mosaic virus (TMV). Both viruses are Tobamoviruses and can be spread by seeds, artificial grafting, human handling, and tobacco products. The virus remains a concern throughout the growing season. The genetic material of ToMV is enclosed within a protein coat. Tomato mosaic virus encodes four different proteins important for virus replication and movement, they are 180 kDa/RNA dependent RNA polymerase, 130 kDa/Methyltransferase/Helicase, 30 kDa/Movement protein and 18 kDa/Coat protein. ToMV spreads mainly through infected seeds, saplings, agricultural tools, and often through the hands of nursery workers who have failed to sanitize themselves properly before entering the fields. It would require only a few infected saplings for the virus to spread over an entire field in a matter of days. A wide range of symptoms include abnormally shaped fruit, fruit lesions, reduced fruit size, distorted growing points, abnormal color (often yellowing), form and patterns on leaves, distorted stems, and distortion and dwarfing of the plant as a whole. ToMV can remain dormant in weeds, and the plant remains around the field and returns later. There is no cure for plant viruses, and management actions should focus on preventing viral spread. This chapter aims to provide readers with a more in-depth understanding of the structure, cell biology, and disease cycle of ToMV, and their control measures for food security.