Objective: To assess changes in barriers to mental health care for children and adolescents over 16 years. Methods: We used data from two nationally representative surveys of Australian children and adolescents (4–17 years old), conducted in 1998 (N = 4509) and 2013–2014 (N = 6310). Barriers to care were assessed among parents who had reported a perceived partially met or unmet need for their child in the past 6 months in 1998, and the past 12 months in 2013–2014; barriers were similarly assessed among adolescents in relation to themselves. We addressed measurement inconsistencies between surveys by harmonising barriers to accommodate differences in wording and performing sensitivity analyses among those with a 1-month disorder to equalise the timeframes in which barriers were assessed. To assess change, we examined whether the rank order of the three most commonly endorsed barriers changed and whether the 95% confidence intervals (CI) around their estimates overlapped. Results: Similar proportions of parents reported a partially met or unmet need in 1998 (12.9%, 95% CI = [11.7, 14.0]) as in 2013–2014 (14.3%, 95% CI = [13.2, 15.3]), but the ratio of unmet to partially met need decreased from 3:1 in 1998 to 1:1 in 2013–2014. Top three parent-endorsed barriers (‘self-reliance’, ‘unsure where to get help’, and ‘cost’) were the same at both time points; ‘self-reliance’ decreased from 65.9% (95% CI = [61.1%, 70.7%]) to 34.9% (95% CI = [31.5%, 38.3%]). Top two adolescent-endorsed barriers (‘self-reliance’ and ‘concerned what others might think’) were the same at both time points, the third differed, but none of them decreased. Conclusion: Perceived unmet need for mental health care for children and adolescents may have decreased between 1998 and 2013–2014, but the gap in receiving sufficient care may have increased. Despite investments in community awareness and treatment during this period, key barriers seemed largely unchanged. For parents, the decrease in self-reliance may reflect a positive shift in beliefs about the potential benefits of treatment.