a young Maine Coon in a bag

When Does A Maine Coon Kitten Become An Adult Cat?

Getting a Maine Coon kitten was sure to have been a memorable day.

All the expectations of how the cute ball of fur will transition into an adult cat.

Maine Coons aren’t average though in many ways and grow over a much longer timeframe than an average breed.

A Maine Coon owner can expect their kitten to continue growing and developing for 3 to 5 years.

But when are they considered an adult, not least for when you might need to transition to adult cat food.

When does a Maine Coon kitten become an adult Maine Coon?

A Maine Coon kitten becomes an adult cat at 12 months old.  Maine Coons mature slower than other breeds, so adult food transition should be between the 12 to 15 month period. After becoming an adult cat the Maine Coon is in the Junior phase of its lifecycle.

Being a kitten is just the first phase of your Maine Coons journey through its life.

While most stages are just the further extension of time, the transition from a kitten to an adult is much more transformative.

Your Maine Coon has left behind the dependence on the mother and is now fully developing into a self-reliant cat, with all the hunting and social skills needed for them to survive.

facial image of a maine coon cat

What Does Being An Adult Mean For A Maine Coon?

An adult cat is defined as “a cat that is fully grown or developed”

Although a Maine Coon is not fully grown at 1 year old, it is fully developed.

The Maine Coon is no longer a kitten after 12 to 15 months old and will continue growing for 3 to 5 years after birth.

Nevertheless, your Maine Coon will have all its skills already learned.

Their health and the immune system are now much more robust for them to cope with the world.

What To Expect As Your Maine Coon Becomes An Adult

A kitten can grow so fast that a Maine Coon can look like an adult cat by the age of 6 months.

A 6 month old Maine Coon could reasonably be expected to be around 3.5kg (8lbs) in weight.

That’s already looking like an adult cat in size and weight at least.

Despite the size, they are still kittens and will require nutritional supplements consistent with their growth phase.

A quality protein rich balanced diet is recommended for a Maine Coon until the 12 to 15 month period.

Transitioning to an adult cat diet should take around 1 to 2 weeks so the digestive system can acclimatize to the changing diet.

Your newly adult Maine Coon will have microbes and bacteria in the gastrointestinal tract that are used to breaking down what it is expecting to eat.

A sudden change to an adult diet can bring on a shock which may result in vomiting and litter tray trips.

Over a two week period, it’s advisable to swap out a portion of kitten food and introduce the adult food gradually as a greater proportion of their diet.

Personally, I did in 25% ratios where the first proportion change was one quarter adult food, and three quarters kitten food.

I then waited for 4 days and moved to a half / half arrangement.

And so on.

The mane on a Maine Coon can lightly start being visible as it becomes an adult as well.

How well it develops is down to environment and genetics.

Even as a Maine Coon kitten transitions into an adult, it is still in the junior phase of its life and will continue to grow for another 2 to 4 years.

Much less noticeable maybe, but it still needs that protein rich diet for the next few years at least.

a maine coon with large ears

The Life Stages For A Maine Coon

As a Maine Coon is born they are quite obviously known as a kitten. It’s the same for every breed.

However, kitten status is just the first stage of six life stages that your Maine Coon will go through.

Briefly, they are;

Kitten (up to 12 or 15 months) – this might be what you call the ‘ball of string’ phase.

As soon as they can walk properly they have a large desire to play and pounce, gaining vital skills in coordination and instincts.

During the early phase, it can be a good time to condition your kitten to handling, grooming, bathing, and pet carriers.

Junior – (12 months to 2 years) – the Maine Coon is now a young adult, the equivalent of a young teenager.

The baby faced youthfulness disappears as they attain physical maturity.

The tomfoolery stops and the emergence of your Maine Coons personality and temperament starts to come through.

Prime – (2 years to 6 years) – the prime stage will be when your Maine Coon reaches its maximum size.

It will stop growing during their prime, and they should be in peak physical condition.

A Maine Coon may develop a mane during this period.

The coat is glossy as well as sleek, and the Maine Coon should be extremely healthy with their senses at maximum ability.

a maine coon kitten playing with tap water

Mature – (7 years to 10 years) – the Maine Coon will start to decrease their physical activity.

If they continue to eat as much as they did before, the cat will gain weight.

The Maine Coon might not want to jump up as much as they did before as their muscles start to deteriorate and aches and pains start to impede physical exertion.

A Maine Coon brought up on a bad diet may start to develop internal problems as their lack of physical health declines.

Senior – (10 years to 14 years) – a Maine Coon as it enters the senior stage of its life might experience profound changes in habits and behavior.

Aches and pains might be much more profound and they will exert themselves much less.

They might start not jumping up to their food table in favor of meowing for you to put it on the floor.

Lumps and bumps might start to develop on the body, and regular checking is advised.

Geriatric – (15 years +) – in the later stages of life, the Maine Coon will keep physical exertion to a minimum.

Often the cat may become more friendly as they realize they are getting old.

a large maine coon relaxing


A Maine Coon kitten becomes an adult cat when they are about one year old, although this can vary depending on who you ask.

Some people say that it’s around two or three years old, but others will argue for as little as nine months.

The only way to know for sure what age your Maine Coon kitty has become an adult is by looking at their health and behavior.

The pet food manufacturers start the adult Maine Coon diet at between 12 and 15 months, so the professionals seem to agree that after one year, your kitten has all grown up and is now a young adult.

About the Author


My name is Ann and I have been looking after and breeding cats since 2013. I am currently the proud ownder of Alita, a female Maine Coon to whom I've dedicated this site. She has had 2 litters and is around 3 years old. We share adventures and stories together.

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Maine Coon 101 | Read This Before Getting One