Northern peatlands are a globally significant source of methane (CH₄), and emissions are projected to increase due to warming and permafrost loss. Understanding the microbial mechanisms behind patterns in CH₄ production in these systems will be key to predicting annual emissions changes, with stable carbon isotopes (δ¹³C-CH₄) being a powerful tool for characterizing these drivers. Given that δ¹³C signatures of CH₄ are used in top-down atmospheric inversion models to partition sources, our ability to model CH₄ production pathways and associated δ¹³C-CH₄ signatures in peatland types impacted by a changing climate is critical. We sought to characterize the role of environmental conditions, including both hydrologic and vegetation patterns associated with permafrost thaw, on δ¹³C-CH₄ signatures from a diverse set of high-latitude peatlands. We measured porewater and emitted CH₄ stable isotopes, pH, and vegetation composition from five boreal-Arctic peatlands. Porewater δ¹³C-CH₄ was strongly associated with peatland type, with δ¹³C enriched values obtained from more minerotrophic fens (-61.2 ± 9.1‰) compared to permafrost-free bogs (-74.1 ± 9.4‰) and raised permafrost bogs (-81.6 ± 11.5‰). Variation in porewater δ¹³C-CH₄ was best explained by sedge cover, CH₄ concentration, and the interactive effect of peatland type and pH (r² = 0.50, p < 0.001). Emitted δ¹³C-CH₄ varied greatly but was positively correlated with porewater δ¹³C-CH₄, suggesting that porewater data can be used to predict changing emissions signatures from these systems. We calculated a weighted mean mixed atmospheric CH₄ signature for northern peatlands of -65.3 ± 7‰ and show that this signature is more sensitive to landscape drying (4 to 10 % depletion in δ¹³C) than wetting (1.5 to 5% enrichment in δ¹³C) under permafrost thaw scenarios. Our results suggest northern peatland δ¹³C-CH₄ signatures are likely to shift in the future which has important implications for source partitioning in atmospheric inversion models.