Our objective was to conduct a systematic review and meta-analysis of studies assessing the diagnostic performance of (18)F-fluorodeoxyglucose positron emission tomography (FDG PET) with or without computed tomography (CT) in post-treatment response assessment and/or surveillance imaging of head and neck squamous cell carcinoma (HNSCC). A systematic search of the indexed medical literature was done using appropriate keywords to identify relevant studies. Metrics of diagnostic test accuracy, viz. sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were extracted from individual studies and combined using a random effects model to yield weighted mean pooled estimates with 95% confidence intervals (95% CI). The impact of timing of post-treatment scan, study quality and advancements in PET technology was explored through meta-regression. A total of 51 studies involving 2,335 patients were included in the meta-analysis. The weighted mean (95% CI) pooled sensitivity, specificity, PPV and NPV of post-treatment FDG PET(CT) for the primary site was 79.9% (73.7-85.2%), 87.5% (85.2-89.5%), 58.6% (52.6-64.5%) and 95.1% (93.5-96.5%), respectively. Similar estimates for the neck were 72.7% (66.6-78.2%), 87.6% (85.7-89.3%), 52.1% (46.6-57.6%) and 94.5% (93.1-95.7%), respectively. Scans done ≥ 12 weeks after completion of definitive therapy had moderately higher diagnostic accuracy on meta-regression analysis using time as a covariate. The overall diagnostic performance of post-treatment FDG PET(CT) for response assessment and surveillance imaging of HNSCC is good, but its PPV is somewhat suboptimal. Its NPV remains exceptionally high and a negative post-treatment scan is highly suggestive of absence of viable disease that can guide therapeutic decision-making. Timing of post-treatment imaging has a significant, though moderate impact on diagnostic accuracy.