Before I start, I have to mention that I am still pretty new to this myself, but I hope to provide some good information for those interested in breeding Chinchillas. Please remember before you decide to breed that you will be responsible for finding each and every kit a good home. Do a lot of research before you breed to lessen the risk of any complications. And most importantly, be sure you are breeding good quality animals. The only reason to breed any animal is to improve the species overall. So you should NEVER breed poor quality animals, animals for which you have no background information, or animals which may have genetic diseases. We must always work toward improvement by breeding chinchillas with good type, good personalities, good health, and good size.
If you cannot put this effort into your breeding program, please do not breed.

Chinchillas reach puberty anywhere from 4 to 8 months of age. However, it is not impossible for an 8 week old female to come into heat and get pregnant. Nor is it impossible for a male to impregnate a female at 8 weeks old. It is very irresponsible to allow opposite-sex chinchillas of this age to live together. It is extremely dangerous for females to be pregnant this young because they are still growing until they are 8 months to a year old. A female this small and this young cannot handle a pregnancy and often times these cases result in heartbreak. A female can be safely bred if she is at least 8 months to a year old, and at least 600 grams. Females smaller than this should not be bred because there is a high risk that she will have a difficult pregnancy due to her size. Males also should not be bred much before they are this age because there is no way to completely know his quality, size, and temperment this early. When both chinchillas are of the right age and size, the male and female can be introduced. Do this slowly and carefully and be sure to watch them and make sure no fighting will occur. When they are first introduced there may be some jumping around, maybe some fur flying, but as long as neither chin is being aggressive to the other, they should be fine. You can start by letting them spend time together for 10-15 each day, until they seem used to each other. It is not recommended to allow a female to have more than 2 litters per year as any more would be very hard on her.

The female's heat cycle occurs about every 28 days, and lasts 3-4 days. During this time she may be slightly more aggressive and more likely to spray urine. The vaginal openning becomes moist and redish, and she may expel a small waxy estrus plug.

When mating does occur, the male will often make cooing noises to the female. It usually takes place during the night, and the next morning you will probably find fur all over the cage and possibly the mating plug, which is a waxy plug larger than the estrus plug. The male should be checked after mating for hair rings around the penis (however, any male of breeding age, whether breeding or not, should be checked at least every month for hair rings). The males are usually pretty good about cleaning this up, but since so much hair is lost during mating it is a good idea to check him and remove any hair found around the penis.

The gestation period of the female is about 111 days. By about 90 days her belly should look enlarged, and her nipples will be red and swollen. Monitoring weight gain is the best way to tell if she is pregnant, do not try to feel the babies in her belly, this can harm them. You can however, rest your hand gently on her belly, and you will sometimes feel the babies kicking. A nest box should be provided in the bottom of the cage and shavings to allow her plenty of privacy and comfort to have her kits.

Birth usually takes place at night, and the female may become aggressive toward the male before it takes place. She also may not want to eat. Labor usually lasts about a half hour, and if it's more than an hour, call a vet. She will deliver each kit separately and clean them and warm them. If you notice her having any trouble, get her to a vet. Dad should be removed from the cage by this point to avoid a breedback (pregnancy immediately following delivery), and he can go back after 10 days as long as he does well with the kits, and you are ready for her to have another litter. Do not give her a dust bath for 7-10 days after giving birth.

The kits are born fully developed, fully furred, and eyes and ears open. They should immediately crawl under her for warmth and food. Female chins stand to nurse, not lying on their side like some small animals. Be sure to watch the family carefully to make sure dad is not aggressive toward the newborn kits. Most male chins make great dads and will help mom take care of the new little ones. It is important to start handling and socializing the kits in the first few days if the parents are okay with it. They will not reject the babies if they have human sent on them like some animals. Monitor weight gain very carefully and make sure the kits continue to gain. They may loose a gram or two in the first day, or stay the same, but should start gaining after the first day. By 3 weeks old the weight should double from what it was at birth. The kits will soon begin eating hay and pellets along with mom's milk. The babies can begin to be weaned at 6-8 weeks old, but may stay with the parents until 10 weeks. Here is a picture of a newborn kit, just hours old. They are about the size of a hamster.

Be sure to take breeding very seriously and know that you may have to call a vet if their are any complications observed. You are responsible as a breeder or pet owner for the well-being of the parents and kits. The kits are cute and fun to have, but it is not always an enjoyable hobby. Problems can arise, and the kits and even the mothers do not always survive. These situations are very heart-breaking, so please keep this in mind when deciding whether or not to breed.