Background Previous studies have found sensory processing abnormalities, behavioural, and emotional challenges in children with developmental disorders, particularly autism spectrum disorder (ASD) and attention deficit hyperactivity disorder. There is little research on the sensory, emotional, and behavioural differences between individuals with autism spectrum disorder and attention-deficit/hyperactivity disorder (ADHD) across age cohorts. Aim This study examined the correlation and differences in sensory processing, emotional, and behavioural challenges in children with autism spectrum disorder, attention-deficit/hyperactivity disorder (ADHD), and typically developing children. This study also examined these characteristics in two age groups: 4–11-year-olds and 12–18-year-olds. Methodology The study included 362 mothers of their children among three groups: 123 with ASD, 100 with ADHD, and 139 from the typical population. The Short Sensory Profile (SSP) and Child Behaviour Checklist were administered to participants along with a demographic profile. The participants were between 25–50. Pearson correlation, MANOVA and MANCOVA were used to fulfil research objectives. Results and discussion The study found a link between tactile sensitivity, sensation seeking, auditory filtering, and behavioural and emotional issues in children with ASD and ADHD. Sensory features also predicted emotional and behavioural issues in these populations. The MANCOVA analysis showed significant variations in sensory processing, behavioural, and emotional issues among populations, controlling for age groups. Conclusion In conclusion, this study shows the need for early diagnosis of sensory processing impairments in these groups and developmental-stage-specific therapies. The study highlights the need for longitudinal research to understand sensory processing patterns, emotional, and behavioural issues, and development, particularly in India.