As the population ages, understanding brain ageing becomes increasingly crucial. Circular RNAs (circRNAs) are a relatively new class of RNA and have emerged as important regulators of gene expression, often functioning as microRNA (miRNA) sponges. Understanding their interactions with miRNAs in the ageing brain can provide insights into their roles in age-related decline and disease. In this study, we profiled circRNAs differentially expressed with age and their interactions with miRNAs in the posterior cingulate cortex (PCC), a brain region that is important for memory and learning and undergoes age-related changes. RNA was extracted from post-mortem PCC tissue from 62 adults (36-103 years), who were free of neurological disease at the time of death. Total and small RNA sequencing (RNAseq) were performed using the same RNA sample/participant, and circRNAs and miRNAs were identified using CIRCexplorer2 and nf-core/smrnaseq pipelines, respectively. After quality control checks, 3258 circRNAs and 843 miRNAs were retained for analysis. Non-linear models were used to identify age-associated circRNAs, adjusting for potential covariates including sex, postmortem interval, neuron proportion, RNA integrity, and pH. A total of 252 circRNAs were significantly associated with age (FDR <0.05). Further, correlations between age-associated circRNAs and miRNAs revealed 843 significant miRNA-circRNA pairs (195 unique circRNAs; 466 unique miRNAs; absolute Pearson’s r > 0.5, FDR < 0.05). Of these, 287 pairs were negatively correlated while 556 pairs were positively correlated. In conclusion, we identified age-associated circRNAs in the PCC across the adult lifespan. We also showed correlations between these circRNAs and multiple miRNAs. These findings suggest a potential regulatory mechanism of circRNAs in brain ageing. Future studies will focus on unravelling the interplay between circular RNAs and miRNAs in the context of brain ageing.