Recent radio observations reveal the existence of mini-radio lobes in active galaxies with scales of ∼10 pc. The lobes are expected to be filled with shock-accelerated electrons and protons. In this work, we examine the photon spectra from the mini-lobes, properly taking the hadronic processes into account. We find that the resultant broad-band spectra contain the two distinct hadronic bumps in γ-ray bands, i.e. the proton synchrotron bump at ∼1 MeV and the synchrotron bump at ∼1 GeV due to the secondary electrons/positrons produced via photo-pion cascade. In particular, when the duration of particle injection is shorter than the lobe age, radio-dark γ-ray lobes are predicted. The existence of the γ-ray lobes could be testable with the future TeV–γ Cherenkov Telescope Array.