To gain insights into the magnetic interactions in ferromagnetic R 2 Mn 2 O 7 pyrochlores (R = rare earth element), we systematically investigated the effects of magnetic dilution in the (Dy 1−x Lu x ) 2 Mn 2 O 7 system by gradually increasing the concentration of nonmagnetic Lu 3+ ions at the R-cation site. Single-phase samples were successfully obtained for the entire substitution range of 0.0≤x≤1.0 through ultra-high-pressure synthesis. All the samples display sharp increases in both dc and ac magnetic susceptibilities below ∼40 K, followed by an appearance of FC–ZFC irreversibilities and broad frequency-dependent maxima at lower temperatures, indicative of a re-entrant spin–glass like behavior. With increasing x, both the ferromagnetic transition temperature and the cusp temperature in the ZFC susceptibility curve were found to get monotonically lowered. It was concluded that Dy 3+ –Dy 3+ and/or Dy 3+ –Mn 4+ magnetic interactions affect the magnetic properties of (Dy,Lu) 2 Mn 2 O 7 .