Aim: Cerebral venous sinus thrombosis (CVST) is a rare but serious complication of paediatric mastoiditis. An apparent increase in CVST cases was noted post-COVID. This study examined CVST incidence over a seven-year period spanning the pre- and post-COVID eras and explored associated trends. Methodology:A retrospective cohort study included all children admitted with mastoiditis to a tertiary paediatric hospital from 2018–2024. Data collected included demographics, imaging, CVST diagnosis, and microbiology. Pre-COVID cases (2018–2020) were compared with post-COVID cases (2021–2024). Results: 115 mastoiditis cases were identified, with 43 pre-COVID and 72 post-COVID. Demographics were similar between groups. CT / MRI utilisation increased significantly from 40% (17/43) pre-COVID to 78% (37/46) post-COVID (RR 1.97, 95% CI 1.33–2.90; p < 0.001). Among children who underwent scanning, CVST was detected in 3/17 (17.6%) pre-COVID and 15/56 (26.8%) post-COVID—a 52% relative increase. This difference did not reach statistical significance (RR 1.52, 95% CI 0.50–4.64; p = 0.46), likely reflecting the small pre-COVID cohort. Streptococcus pneumoniae remained the most common pathogen, with increased Streptococcus pyogenes and polymicrobial infections observed post-COVID. Conclusion: CT imaging increased significantly post-COVID, revealing a higher, though not statistically significant, rate of CVST among scanned children. There was also a post-pandemic trend toward more polymicrobial infections and a greater prevalence of Streptococcus pyogenes. Optimised imaging pathways may support earlier detection and improved outcomes.