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Tillage generally reduces aggregation and particulate organic matter (POM) content. We hypothesized that reduced C sequestration in conventional tillage (CT) compared with no‐tillage (NT) is related to differences in aggregate turnover. Four soils (Haplustoll, Fragiudalf, Hapludalf, and Paleudalf), each with NT, CT, and native vegetation (NV) treatments, were separated into aggregates. Free light fraction (LF) and intraaggregate POM (iPOM) were isolated. At one site we used ¹³C natural abundance to differentiate crop‐ and grassland‐derived C. Concentrations of coarse iPOM C (250–2000 μm iPOM in macroaggregates), expressed on a per unit aggregate weight (g iPOM C kg⁻¹ aggregate), did not differ between tillage treatments. In contrast, concentrations of fine iPOM C (53–250 μm iPOM in macroaggregates) were less in CT compared to NT macroaggregates. On a whole soil basis, fine iPOM C was on …