Although the adults spend most of their time on land, the females enter ponds and other still waters to lay their eggs, toad spawn, which can be distinguished from the spawn of the common frog as it forms strings rather than a large mass of eggs. Although males usually wait for females at breeding sites, they will sometimes try to ambush them before they reach the water. Males clamber onto the backs of females and hold onto them tightly (a posture known as amplexus), the nuptial pads on their fingers providing extra grip. Over-eager males sometimes grab another male, however, the captured males croak soon informs them of their mistake.

Common toads spawn amongst waterweed. The female toad releases long strings of triple-stranded eggs, which the male on her back fertilises with sperm. About 600 - 4000 eggs are laid. These strings become twisted and stretched around waterweed and vegetation so that the eggs settle into two strands. A few days later the adults leave the water. The tadpoles hatch within 10 days and despite being distasteful to most predators, the majority will not reach adulthood. The tadpoles metamorphose into toadlets within 2 - 3 months - varying according to food availability and water temperature. The young tadpoles resemble other tadpoles in their appearance except that toad tadpoles have a larger, rounder blacker head and shorter tail. They leave the water in May. Common toads reach sexual maturity at 4 years of age. The life span of a Common Toad in captivity may be as high as 20 - 40 years, however, in the wild, it is more likely to be 10 - 12 years.