These salamanders are slender, with a wide nose and distinctive long toes, and range in size from 11 to 18 cm (4.3 to 7.1 in).

Eggs are laid in small agglomerations attached to submerged twigs or other natural support at the pond's edge.

Often in cooler conditions, the LJ or LJJ female may mate with the Jefferson salamander male and only "borrow" his sperm to trigger genetic cloning of herself, not adding his chromosome (J) to the DNA of the embryo.

The secretive adults tend to hide under stones or logs, or in leaf litter and other underbrush in deciduous forests during damp conditions.

They are usually not found in conifer forests, likely due to the dryness and prickliness of some pine and spruce needles, which may injure amphibians with their thin skins.

They must get below the frost line (about 18 inches)[citation needed] in order to survive winter conditions in northern latitudes.

The breeding sites they choose are fishless ponds and vernal pools, filled with spring snow meltwater in northern latitudes.

Jefferson salamanders are one of the first amphibians to emerge in springtime at the northern edge of their range in southern Ontario where they are seen "snowshoeing" across the still frozen understory of the forest to reach partially melted breeding ponds.