Autism Symptoms Checklist: Recognize the Signs Early and Take Action

Autism symptoms (also called autism signs, autism traits or ASD symptoms) are differences in social interaction, communication, repetitive behaviours, sensory processing and emotional responses. Learn what to look for and take the first step today.

So what are the early signs of autism, and why do they matter? You may be wondering whether your child is finding certain areas harder than other children. You may also have noticed that your child is reaching some emotional, social and behavioural milestones on a different timeline (check out our Development assessment tools for children). Before you ask your doctor “Does my child have autism?”, you can start by noting what you see at home using this Autism Symptoms Checklist.

What Are the 3 Main Symptoms of Autism?

The 3 main symptoms of autism are differences in social interaction, differences in communication, and repetitive behaviours or deep, focused interests. Sensory differences, such as strong reactions to sounds, lights or textures, are also part of an autism diagnosis. These autism spectrum disorder symptoms look different in every child.

Taking the Autism Online Test

On this page you will find the detailed autism symptoms checklist with a downloadable PDF file. But if you are wondering whether you or your child is autistic, why not save time and take the Autism Test Online? This test compares your answers (or your child’s) against the known signs of autism, Asperger’s or ADHD and gives you a report you can take to your doctor. It is a screening tool, not a diagnosis. Use the test wizard below to guide you to the right test. Otherwise, scroll down and keep reading.

Key Signs of Autism

Key signs of autism include differences in social interaction, speaking or understanding language, repeated behaviours, strong sensory reactions, and intense focus or big emotions. Before we go through the detailed autism symptoms, let’s take a quick look at some of the key signs of autism in babies (under 2.5 years), toddlers (2.5 to 5 years) and children (5 to 12 years). This is when most autistic children are diagnosed.

Autism Signs in Babies

Early signs of autism in babies can include no social smiling by 6 months, no babbling or gestures by 12 months, and no two-word phrases by 24 months. A baby may make less eye contact, not point to share interests, or become strongly attached to particular objects. Other signs include not responding to sounds or their name, and losing skills they already had. Any loss of skills is worth raising with your doctor straight away.

Fig 1: Early signs of autism in babies. Keep an eye out for these symptoms.

Autism Symptoms in Toddlers

Autism symptoms in toddlers can include finding it hard to express needs, playing alongside rather than with other children, and reaching some milestones later. They may make less eye contact, not enjoy cuddling or pretend play, and often feel safest when routines stay the same. Some toddlers repeat words or phrases (echolalia, which is a form of communication), laugh at unexpected times, or play in a repetitive way.

They might react strongly (or very little) to sound, touch or pain, attach strongly to objects, or find it hard to start and keep a conversation going. Other signs include spinning, hand flapping, constant running, or hurting themselves when overwhelmed. Self-injury is a sign of distress, so it is always worth talking to your doctor about.

Autism Signs in Children

Signs of autism in children can include laughing at unexpected times, not seeming to notice danger, and reacting to pain differently from others. They may avoid eye contact, not want cuddles, or enjoy time alone. Some children repeat words, play in their own way, or get very upset when plans change. They may seem not to hear sounds, love spinning objects, or find it hard to talk and play with others in the expected way.

How to Use this Autism Symptoms Checklist

As soon as you notice that some of the developmental skills above seem to be missing or slow to appear, start the assessment below. Children change quickly, so repeat it as your child grows. At Autism 360, we recommend the following plan:

If Development Looks on Track

• Do the first assessment (using the checklist below) when your child is 18 months old
• If nothing stands out, do the next assessment when your child is 24 months (2 years) old
• Do a final screening at 36 months old

Note that autism in girls can look quite different from autism in boys. Many girls mask or camouflage their traits, so autism signs may not be obvious until they reach their early teens.

If You Notice Some Differences

• Do the first assessment when your child is 18 months old.
• If some answers stand out, do the next assessment when your child is 20 months old.
• This time, look closely at what has changed since the previous screening.
• If you believe your child may have autism, go to the end of this article to take a formal Autism Test.

Examples of How to Use the Checklist:

Whether or not you see repetitive patterns, make a note of anything that might be contributing. This may seem tedious at first, but the information that only you can gather is invaluable if your child needs a formal assessment. You know your child! Your notes help the doctor recommend the right developmental tools for your child.
You can either bookmark and print this page or download a FREE autism symptoms checklist soft copy using the PDF link. Print a few copies and keep the results together in a folder. Date each form so you can compare over time.

Table 1: The Autism Symptoms Checklist: identifying the 60 signs of autism in kids

As you can see, outside events such as moving house or a new sibling can affect your child’s behaviour. In these situations, repeat the assessment every month. Every child needs time to adjust to big changes in their life and daily routine. At the same time, you don’t want to put everything down to “just a phase” if something more is going on. Early diagnosis and the right support give your child the best start.

What are the symptoms of mild autism in toddlers, children, and adults?

Here are common mild autism symptoms, broken down by age group. (“Mild” usually means lower support needs. It doesn’t mean life is always easy for that person.) Mild autism symptoms are often described as autism level 1 symptoms, the DSM-5 term for autistic people who need some support.

Mild Autism Symptoms in Toddlers

1. Less eye contact
2. Speech or language developing later
3. Not always responding to their name
4. Preferring to play alone rather than with others
5. Repetitive movements like hand flapping or rocking
6. Sensitivity to sounds, textures or lights

Mild Autism Symptoms in Children

1. Finding it hard to make or keep friends
2. Reading social cues or emotions differently
3. A strong need for routine, with change feeling distressing
4. Deep, focused interests (for example, trains or numbers)
5. Repetitive behaviours like lining up toys or repeating phrases
6. May speak clearly but find back-and-forth conversation harder

Mild Autism Symptoms in Adults

1. Finding social interaction or small talk tiring or confusing
2. Taking sarcasm, jokes or body language literally
3. Strong focus on specific interests or hobbies
4. Preference for routines and predictability
5. Sensory sensitivities (for example, crowded places or loud noises)
6. Anxiety or overwhelm in social situations

Autism Traits and Strengths to Notice Too

Checklists focus on challenges, but traits of autism often come with real strengths. While you are noting autistic symptoms, also write down what your child loves and does well. Many autistic children have:

• Excellent memory for facts, routes, songs or details others miss
• Deep focus and knowledge in areas they love
• Honesty and a strong sense of fairness
• Strong visual thinking, pattern spotting or puzzle-solving skills
• A playful, unique sense of humour

These strengths matter. They tell you how your child learns best, and good support builds on them.

What to Do If You Notice Signs of Autism

Seeing several autism signs can feel overwhelming. Here are practical next steps:

1. Write it down. Use the checklist, note dates and short examples, and take a few videos of the behaviours you are unsure about. This helps your doctor see what you see.
2. Book a GP appointment. Share your notes and ask about a referral to a paediatrician or a team that does autism assessments.
3. Don’t wait to start helping. You don’t need a diagnosis to make home easier. Keep routines predictable, use simple visuals for the day, and lower noise and light when your child is overwhelmed.
4. Treat behaviour as communication. When your child melts down, flaps or withdraws, ask “what is this telling me?” before “how do I stop it?”.
5. Follow your child’s lead. Join in with what they love. Shared play around their interests is one of the best ways to build connection and communication.
6. Look after yourself. Talk to other parents and find support for you too. You can’t pour from an empty cup.

How to Interpret the Checklist Results

24 Yes + 15 Repetitive = 50% Chance

As a rough guide on our checklist, if you answer “Yes” to at least 40% of the questions (24) and at least 25% (15) of those behaviours are repetitive in nature, then there is more than a 50% chance that your child may be autistic. This checklist is not a diagnosis, and only a qualified professional can diagnose autism. Before you worry, go to our Autism Test Center and try one of the following tests based on your child’s age.

Autism Test for Toddlers (age 2.5 to 5)

Autism Test for Children (age 5 to 12)

FAQs on Autism Symptoms

Reference:
https://www.cdc.gov/autism/signs-symptoms/index.html

Ash Bhattacharya

I am Ash and I celebrate Neurodiversity! Growing up with an elder brother with severe Autism was tough – but it has also taught me essential life lessons. I don’t believe that people with Autism are necessarily or have any disorder (except in extreme cases). They are just different! And that is something to be proud of! I am passionate about helping other families who may have Autism conditions in their family. So please reach out and drop me a note. I will be glad to help 🙂