Parents may first note ASD behaviours in young children. Some behaviours may be recognised only at the school-going age. Not all individuals with ASD exhibit these behaviours, but most will display several symptoms. The two main domains of behaviours are characterised as "deficits in social communication and interaction" and "restricted/ repetitive behaviours".

Social communication / interaction behaviours may include:

• Atypical responses in display of emotions (e.g., anger, distress to show affection)
• Difficulties adjusting to changes in a routine, or being in an overlay stimulating environment
• Difficulties engaging in reciprocal conversation
• Echolalia - repeating words or phrases 
• May speak in an unusual tone of voice or accent that might sound sing-song or flat
• Poor joint attention - appear to not share enjoyment of activities or objects with others
• Poor initiation and maintenance of eye contact
• Poor in using non-verbal communication to regulate social interaction. E.g., lacking gestures, facial expressions, standing at an awkward distance
• Poor response to someone calling their name
• Poor perspective taking, has difficulties comprehending social problems from another person's point of view. Difficulties deciphering non-verbal communication from others
• Preoccupied with a certain topic; poor social awareness of their communication partner
• Using words that are not commonly used in a normal conversational context

Restrictive / repetitive behaviors may include:

• Intense interest in a specific topic or object (such as numbers, transportation, details, or facts) 
• Tendency to repeat certain behaviours such that the frequency is deemed unusual

Individuals with ASD may also experience sensory processing difficulties, such as, being overly sensitive to light, movement, loud noises, textures of clothing, and/or temperature. They may also have sleep and/or digestive problems, and sensitive temperaments. 

Despite their challenges, individuals with ASD also have many strengths and abilities. 

Symptoms manifest differently and vary in individuals. Hence, treatment plans need to be tailored to suit the individual’s and their family’s needs. In general, individuals with ASD respond well to the following treatment:

• Behavioural Training and Management that focuses on using positive reinforcement, functional communication, socio-emotional, and social skills to improvement overall symptoms. This includes: Applied Behavioural Analysis (ABA), Treatment and Education of Autistic and Related Communication Handicapped Children (TEACCH), and sensory integration.
• Parent Training and Community Support.
• Pharmacotherapy for co-morbid mental health disorders.
• Specialised Therapy: Speech and Language Therapy, Occapational Therapy, Educational Therapy, Physical Therapy.