The Peccei-Quinn mechanism remains probably the most compelling explanation of the CP problem of QCD. An inevitable consequence of this mechanism is the existence of axions, light pseudo Nambu-Goldstone bosons which may play a relevant role in astrophysics and cosmology. After an introduction to the topic, I'll present a brief overview of current direct and indirect searches. Finally, I'll discuss some effects that axions (or axion-like particles) might have on the spectra of high-energy astrophysical gamma-ray sources with interesting observational perspectives.