Before the cubs are born, the vixen will prepare one or more natal dens in which to give birth. While these might be dug by herself, she much more commonly renovates an abandoned earth made by a badger, woodchuck or other similarly sized animal. The vixen finally decides on a den in which to give birth based on factors such as good drainage, proximity to food and water, how well concealed it is, etc. A few weeks after birth, the kits may be relocated to the other dens several times.

The normal gestation period varies between 49 and 56 days with the average being 52. As many as thirteen cubs may be born although a typical litter numbers about five. The offspring, called cubs, kits, pups, or whelps have a birth mass between 70 and 120 g. During the first two weeks, when the mother constantly remains with the kits to nurse them and keep them warm, she relies on her mate for any food she herself needs. Helpless and blind at birth, they are entirely dependent on her for their sustenance. This nourishment comes in the form of the vixen´s milk, which according to Rebecca Grambo´s ´The Nature of Foxes´ is three times richer than cow´s milk.

Young red fox kits, shortly after leaving the den for the first time.

The kits develop very rapidly, tripling their weight in ten days. Their bluish grey eyes are open by their second week and the mother is able to leave them for brief periods of time. By the third week, the cubs are capable of moving around, and over the next ten days they begin viciously fighting amongst themselves to establish an order of dominance. It is also within this third week that the cub´s first milk teeth start coming in, although they will need another three weeks to acquire their complete set of twenty-eight. By week four, weaning begins. The kits are fed partially digested food, regurgitated by their parents. Although they are not yet able to eat solid food, the kits will also begin sucking on small pieces of meat, acquiring a taste for things to come. The mother still nurses her young, but will soon begin to discourage this by lying on her stomach when they try to feed.

The kits first leave the den by their fourth or fifth week. When they first appear, they are covered not by the familiar red fur of their parents, but by a sandy, grey-brown pelage that camouflages them well against the soil surrounding their home. By this time, a hierarchy amongst the cubs has been fully established, and they settle into the most carefree time of their lives. At first they don´t stray far from the den, ready to run back upon hearing a warning bark from their parents. They gradually become bolder and begin to explore their world. The kits delight in pouncing on insects, carrying around unusual sticks, leaves, or stones, and in rough housing with their siblings. They frequently stalk and chase one another, or will pounce on a sleeping brother or sister for fun. Some rivalry is still apparent amongst the kits, and they will still fight amongst themselves to get the most food. Nevertheless their play is not the aggressive dominance-related combat previously mentioned, but a method to learn hunting and fighting techniques needed in later life. This behaviour is almost puppy-like, and the previously mentioned body language such as the ´let´s play!´ posture ( head and front paws crouched low with the rump and tail wiggling around high in the air) or food begging gestures (nipping at the parent´s mouths) would appear familiar to a dog owner.

By the second month the kits are fully weaned, and by the third month they are able to catch small prey such as insects. As Summer arrives, the grey juvenile coat has yielded to the reddish hue of their parents, and the kit´s blue eyes have turned the golden colour adults. In addition to play, the kits begin accompanying their parents on hunting trips to sharpen their skills. At six months, a young red fox is fully grown and has most of the skills it needs to survive.