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 five-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:Seventy-seven mastoiditis cases were identified, with 31 pre-COVID and 46 post-COVID. Demographics were similar between groups (median age 2 vs 3 years; male 48.3% vs 67.3%). CT utilisation increased significantly from 45% (14/31) pre-COVID to 80% (37/46) post-COVID (RR 0.56, 95% CI 0.37–0.85; p = 0.003). Among children who underwent CT scanning, CVST was detected in 3/14 (21%) pre-COVID and 18/37 (48%) post-COVID—a 128% relative increase. This difference did not reach statistical significance (RR 0.44, 95% CI 0.15–1.27; p = 0.113), 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.