Abstract Iron is almost ubiquitous in mineral dust aerosol particles and is known to catalyze the photochemical degradation of organics. For the first time we measured the loss of organics in aerosol particles containing various mineral dusts, using citric acid as an organic proxy. For most of the dust‐containing particles, a pronounced mass loss of citric acid was observed after the start of illumination, which we attribute to photochemical processes with iron as catalyst. We present evidence for two pathways of iron‐catalyzed photochemical processing, namely homogeneous through iron leached from dust particles and heterogeneous through iron residing on dust particle surfaces. While these mechanisms are not expected to affect the global budget of organic species in the atmosphere, they can lead to marked reductions in the thickness of organic coatings acquired by airborne mineral dust via condensation of secondary organic compounds, thus affecting their ability to act as ice‐nucleating particles.