Attending appointments is vital for children with special needs, as such appointments involve long-term interdisciplinary care to ensure continuity of care and improve health and well-being. This study was performed to determine the prevalence of missed clinic appointments and identify the factors among those who have ever missed appointments and barriers of access to children’s special needs services at the Child Development Centre (CDC) at the Universiti Kebangsaan Malaysia Medical Centre (UKMMC). Moreover, suggestions for improvement from the caregivers’ perspectives were explored. This is an explanatory sequential mixed methods study among caregivers of children with developmental disabilities aged up to 17 years old. Of 197 caregivers, 62 (31.5%) had missed clinic appointments. Forgetfulness was the most frequently cited reason. The bi-variable analysis showed significant differences in missed appointment rates by gender of caregivers and duration of follow-up. The final logistic regression model demonstrated that, when combined with the effect of being a male caregiver as an independent variable, follow-up duration of more than 6 years increased 2.67 times the risk of missing an appointment. Caregivers’ perceived barriers were transportation, caregiver, child and healthcare services factors. Policies and strategic plans should be focused on key findings from these factors to improve appointment adherence and accessibility to services for children with special needs.