Abstract Background Lifelong inflammation – known to be associated with many non-communicable diseases – has not been thoroughly investigated in hearing. We aimed to determine if glycoprotein A (GlycA), a novel biomarker of chronic inflammation, is associated with hearing acuity in mid-childhood and mid-life. Methods Population-based cross-sectional study within the Longitudinal Study of Australian Children with plasma GlycA and audiometry data (1169 children and 1316 parents). We calculated high Fletcher Index (mean threshold across 1, 2 and 4 kHz), defining hearing loss as threshold >15 decibel hearing level (dB HL) (better ear). Linear/logistic regression quantified associations of GlycA with hearing threshold/loss. Results Mean [standard deviation (SD)] high Fletcher Indices (dB HL) were 8.0 (5.7) for children and 13.1 (6.9) for adults, with 8.7% and 26.1% respectively showing hearing loss. 1-SD rise in GlycA (children 0.13 mmol/L, adults 0.17 mmol/L) predicted higher hearing thresholds for the lower individual frequencies [1 kHz: children β 0.8, 95% confidence interval (CI) 0.3–1.3; adults β 0.8, 95% CI 0.2–1.4]. This same pattern was evident for the high Fletcher Index (children β 0.7, 95% CI 0.3–1.1; adults β 0.8, 95% CI 0.3–1.4). This translated into 1-SD rise in GlycA predicting adult hearing loss [odds ratio (OR) 1.2, 95% CI 1.0–1.5] with similar but attenuated patterns in children. Conclusions GlycA is associated with poorer hearing by mid-childhood. This potentially reframes hearing loss as a life-course condition with inflammatory antecedents common to other non-communicable diseases. Replication and mechanistic studies could inform causal inference and early prevention efforts.