  Short-lived mediators are often used to describe dark matter interactions
with Standard Model particles. When the dark matter mass is heavier than the
mass of the mediator, it may self-annihilate into short-lived mediators, and in
some cases this might be the dominant annihilation channel. This scenario is
known as secluded dark matter. We use Fermi-LAT observations of dwarf
spheroidal galaxies, H.E.S.S. data from the Galactic center, and Planck
measurements of the Cosmic Microwave Background to constrain secluded dark
matter. We explore the interplay between these experiments and we assess the
impact of the mediator mass on our bounds, an often overlooked yet very
important point. In particular, we exclude pair -annihilation cross-sections
greater or on the order of $\sigma v \sim 4 \times 10^{-27} {\rm cm^3/s}$ for
dark matter masses around $10$~GeV and greater or on the order of $\sigma v
\sim \times 10^{-25} {\rm cm^3/s}$ for dark matter masses around a TeV. Our
findings supersede previous constraints which use Fermi-LAT data, and
constitute the first limits on secluded dark sectors using the H.E.S.S.
telescope. We also show that one can fit TeV gamma-ray observations from
H.E.S.S. with secluded dark matter annihilations, with the mediator mass
impacting the best-fit dark matter particle mass. Our findings indicate that
any assessment of secluded dark sectors in the context of indirect detection
significantly depends on the choice of the mediator mass.
