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<p>Fatty alcohols (FAs) are major components of surface lipids in plant leaves and serve as surface-active organic aerosols (OAs), which can act as primary biological aerosol particles (PBAPs). To elucidate the origin and formation of secondary fatty alcohols (SFAs) in atmospheric aerosols, their mass size distribution in aerosol samples obtained from a deciduous forest canopy was measured in spring, summer and autumn. The SFAs showed the highest concentration in spring (growing season), with <span class="inline-formula"><i>n</i></span>-nonacosan-10-ol being the most abundant. In spring and summer, the size peak of <span class="inline-formula"><i>n</i></span>-nonacosan-10-ol was in the particle size range <span class="inline-formula">&gt;10.0</span> <span class="inline-formula">µ</span>m, whereas it was in the 1.9–3.0 <span class="inline-formula">µ</span>m range in autumn. The size distribution of <span class="inline-formula"><i>n</i></span>-nonacosan-10-ol did not show any significant correlation with that of the known biogenic tracers of pollen, soil and fungal spores in spring and summer. The overall results, together with SFAs measured in plant leaves, as well as the literature, suggest that SFAs originate mostly from plant waxes and that leaf senescence status is likely an important factor controlling the size distribution of SFAs. This study provides new insights into the possible sources of PBAPs and their effects on the ice nucleation activity of aerosols based on seasonal changes in particle size.</p>