Signs of Autism in a Toddler: Early Red Flags & How to Spot Them

You’ve probably watched your toddler closely, wondering if a certain quirk is perfectly normal or something to flag. The problem is that many early signs of autism—like avoiding eye contact or not responding to a name—can also show up in typically developing children who simply need more time. This guide walks through the concrete red flags, age by age, so you know what to look for and when to seek a professional opinion.

Age range for early signs of autism: 12–24 months ·
Percentage of children diagnosed by age 3: Approximately 40% ·
Common early sign: not responding to name by 12 months: CDC red flag ·
Typical age of first concern reported by parents: 18 months ·
Number of children with autism in the U.S. (2024): 1 in 36 (CDC)

Five key facts, one pattern: the red flags accumulate rather than appearing in isolation.

How do I tell if my toddler has autism?

Observing social communication differences

Social communication differences are often the earliest and most noticeable signs. The CDC’s developmental milestone resources highlight that by 9 months, a baby should respond to their name, make eye contact, and show facial expressions. By 12 months, they should be babbling, pointing, and gesturing. Missing these milestones doesn’t guarantee autism — but it’s a clear signal to pay attention.

• Not responding to name by 12 months is one of the most commonly cited red flags (University of Florida CARD).
• Lack of eye contact or reduced eye contact by 9 months is flagged by the CDC as a concern.
• Delayed or absent babbling, pointing, or gesturing by 12 months is a red flag according to the NHS.
• Loss of previously acquired language or social skills (regression) can occur between 18–24 months (NHS).

Noticing repetitive behaviors and restricted interests

Repetitive behaviors are another core pillar. The University of Florida CARD checklist lists hand-flapping, rocking, spinning, and lining up toys as signs. These actions are not just “quirks” — they can signal that a toddler is seeking sensory input or struggling to regulate their environment.

• Repetitive movements like hand-flapping, rocking, or spinning are listed by Autism Speaks as common signs.
• Strong resistance to changes in routine is noted by the NHS as a behavioral red flag.
• Unusual sensory reactions — to sound, texture, taste, or light — are flagged by the University of Florida CARD.

When to seek professional evaluation

The CDC recommends universal screening at 18 and 24 months. But parents should not wait for a scheduled screening if they notice multiple red flags. The NHS advises consulting a health visitor or GP if concerns arise at any age.

• Early intervention — starting before age 3 — significantly improves outcomes (CDC).
• If your child has lost skills, request an evaluation immediately (Autism Speaks).

What are red flags for autism in a 2-year-old?

Social red flags

By age 2, social differences become more visible because peers are starting to play together, share toys, and point out things they find interesting. A toddler on the spectrum may stand apart — not because they are shy, but because the social “script” doesn’t come naturally.

• Avoids or does not keep eye contact (CDC Stacks PDF).
• Does not respond to name by 9 months is a red flag (Autism Speaks).
• Does not show facial expressions like happy, sad, angry by 9 months (CDC Stacks PDF).
• Does not play simple interactive games like pat-a-cake by 12 months (Autism Speaks).
• Does not share interests with others by 18 months (University of Florida CARD).

Communication red flags

Communication delays are among the most obvious red flags. By 16 months, a toddler should have a handful of words. By 24 months, they should be combining two words into short phrases like “more milk” or “daddy go.” Autism Speaks lists the absence of these milestones as red flags.

• Uses few or no gestures by 12 months (UNM CDD Autism Portal).
• Does not pretend play by 18 months (University of Florida CARD).
• Loss of previously acquired language or social skills (regression) is a major red flag, per Autism Speaks.

Behavioral red flags

Behavioral signs often include repetitive movements, unusual play patterns, and intense reactions to change. The University of Florida CARD notes that repetitive behaviors such as hand-flapping, rocking, spinning, and lining up toys are commonly seen. Sensory sensitivities — to sounds, textures, or light — are also listed.

• Repetitive movements like hand-flapping, rocking, spinning (Autism Speaks).
• Strong resistance to changes in routine (NHS).
• Unusual sensory reactions to sound, texture, taste, light (University of Florida CARD).

What is the biggest red flag for autism?

The most common early red flag: not responding to name

Not responding to a name by 12 months is the single most frequently cited red flag across clinical guidelines. The CDC lists it as a key developmental marker. The University of Florida CARD also includes it. Autism Speaks calls it a “primary red flag.”

• Not responding to name by 12 months is considered a primary red flag (Autism Speaks).
• Lack of eye contact by 9 months is another highly indicative sign (CDC Stacks PDF).
• Loss of language or social skills at any age is a strong signal (NHS).
• No single sign is definitive, but a combination of delays increases likelihood (CDC).

Other critical signs that warrant immediate attention

Regression — loss of words or social skills — is arguably the strongest signal of all. The Autism Speaks website states plainly: “Loss of previously acquired language or social skills at any age is a major red flag.” The NHS echoes this. If your child was saying “mama” and “dada” at 14 months and stopped by 18 months, that is not a phase — it requires immediate evaluation.

• Loss of previously acquired language or social skills is a major red flag (Autism Speaks).
• Regression typically occurs between 18–24 months (NHS).
• No words by 16 months is a red flag per the UNM CDD Autism Portal.

At what age is autism first noticed?

Early signs by age: 12 months, 18 months, 24 months

Autism signs emerge gradually. Some are visible before the first birthday, but most parents report first concerns around 18 months. The Autism Speaks resource notes that many parents notice signs by 18 months.

• Autism can be reliably diagnosed by age 2 (CDC).
• Many parents notice signs by 18 months (Autism Speaks).
• Some children show signs before 12 months, such as reduced eye contact or lack of social smiling (UNM CDD Autism Portal).
• Regression (loss of skills) typically occurs between 18–24 months (NHS).

Screening recommendations from the AAP and CDC

The CDC recommends autism screening at 18 and 24 months. The American Academy of Pediatrics endorses this schedule. But screening is not a diagnosis — it is a first step. If a screening indicates potential delays, the child should be referred for a formal developmental evaluation.

• The American Academy of Pediatrics recommends autism screening at 18 and 24 months (CDC).
• Earlier screening is warranted if risk factors are present (AAP).

What this means: the gap between when parents notice signs (18 months) and when the average diagnosis happens (4–5 years) is far too wide. Earlier referral closes that gap.

What is mild autism in a 2-year-old?

Characteristics of mild autism (Level 1)

Mild autism, or Level 1 autism in the DSM-5, is not “less autism.” It means the child has noticeable social communication difficulties but does not require substantial support. The Autism Speaks resource explains that Level 1 often involves age-appropriate language but trouble with back-and-forth conversation.

• Mild autism (Level 1) often involves subtle social communication difficulties (DSM-5).
• Children may have age-appropriate language but struggle with back-and-forth conversation (Autism Speaks).
• They may have intense interests in specific topics (NHS).
• Reduced eye contact and difficulty understanding social cues are common (CDC Stacks PDF).

How mild autism differs from typical development

The key difference between a neurotypical toddler and one with mild autism is not the presence of a single behavior — it is the context. Many toddlers have tantrums about routines. Many line up toys. But a child with mild autism may do these things to the exclusion of other activities. The Raising Children Network notes that sensory sensitivities are also common.

• Sensory sensitivities (e.g., to sounds, textures) may be present (Raising Children Network).
• Mild autism does not mean ‘less autism’ – support needs vary (clinical consensus).

Common misconceptions about mild autism

A common misconception is that mild autism will “go away” or that the child will grow out of it. That is not accurate. Autism is lifelong, but early intervention can teach compensatory skills that make daily functioning easier.

• Mild autism is not a temporary phase — it is a neurodevelopmental condition that persists into adulthood.
• Children with mild autism often benefit from social skills training and speech therapy (CDC).

What you need to know

“Avoids or does not keep eye contact, does not respond to name by 9 months, does not show facial expressions.”

CDC (Centers for Disease Control and Prevention)

“The main signs include differences in how someone communicates, behaves and reacts compared to those who are not autistic.”

NHS (National Health Service)

“Loss of previously acquired language or social skills at any age is a major red flag.”

Autism Speaks

For a parent reading this at 2 a.m., the choice is clear: track milestones, trust your gut, and push for an evaluation now rather than later. Early intervention is the single best gift you can give your child — and the window is open wider than most people realize.

Frequently asked questions

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