Due to frequent volcanic activity and erosion of dryland soils, magnified by land use after human settlement (c. 870 AD), peatlands in Iceland receive regular additions of mineral aeolian deposits (tephra and eroded material). Hence, their soils may develop not only histic, but also andic characteristics. Yet, mineral aeolian deposition as an environmental determinant of peatlands in Iceland is still poorly understood, not least with regard to the peatlands carbon (C) stores. This study advances our understanding of the impact of tephra deposition on Histosols by elucidating interactions between histic and andic soil properties and their relation with C structure. We compare Histosols from three Icelandic peatlands of different degree of exposure to aeolian deposition by evaluating datasets of their C structure derived by ¹³C NMR spectroscopy, andic soil properties based on selective extractions of Al, Fe and Si, and decomposition proxies C/N, δ¹³C and δ¹⁵N. By applying multivariate statistical methods, we are able to present several important patterns. Soil organic matter of Histosols with andic properties is less decomposed than that of Histosols without notable andic properties. The interaction of andic and histic soil properties seems to impact their C structure by facilitating the formation of organo-mineral complexes, which particularly hamper the decomposition of chemically more labile C groups. Tephra layers appear to serve as protective barriers. The interaction of andic and histic soil properties and the protective role of major tephra deposits, may enable an unusual potential for long-term C stabilization in a natural peatland environment.