Telomere length is increasingly used as a biomarker of long-term life history costs, ageing and future survival prospects. Yet, to have the potential to predict long-term outcomes, telomere length should exhibit a relatively high within-individual repeatability over time, which has been largely overlooked in past studies. To fill this gap, we conducted a meta-analysis on 74 studies reporting longitudinal telomere length assessment in non-mammalian vertebrates, with the aim to establish the current pattern of within-individual repeatability in telomere length and to identify the methodological (e.g. qPCR/TRF, study length) and biological factors (e.g. taxon, wild/captive, age class, species lifespan, phylogeny) that may affect it. While the median within-individual repeatability of telomere length was moderate to high (R = 0.55; 95% CI: 0.05-0.95; N = 82), marked heterogeneity between studies was evident. Measurement method affected strongly repeatability estimate, with TRF-based studies exhibiting high repeatability (R = 0.80; 95% CI: 0.34-0.96; N = 25), while repeatability of qPCR-based studies was only half of that and more variable (R = 0.46; 95% CI: 0.04-0.82; N = 57). While phylogeny explained some variance in repeatability, phylogenetic signal was not significant (λ = 0.32; 95% CI: 0.00-0.83). None of the biological factors investigated here had a statistically significant association with the repeatability of telomere length, being potentially obscured by methodological noise. Our meta-analysis highlights the need to carefully evaluate and consider within-individual repeatability in telomere studies to ensure the robustness of using telomere length as a biomarker of long-term survival and fitness prospects.