The nuclear spin‐lattice (1/T1) and spin‐spin (1/T2) relaxation rates have been measured for19F nuclei with no magnetic near neighbors (F0) in diluted antiferromagnetic MnxZn1−xF2and FexZn1−xF2, for x between 0.1 and 0.8. ForT≫Tn, 1/T1in FexZn1−xF2varies nearly as x1/2. This result indicates that the relaxation process is dominated by the electron‐nuclear dipole interaction with electronic spins in exchange‐coupled clusters. In contrast, 1/T1in MnxZn1−xF2is independent of x, for x greater than 0.5. As x decreases, 1/T1increases until a maximum is observed at x≃0.1. The departure from x1/2behavior is found to be proportional to x(1−x)8, indicating that the exchange‐isolated Mn electronic spins dominate the nuclear relaxation for x less than 0.4. The absence of the exchange‐isolated electronic spin contribution 1/T1in FexZn1−xF2is attributed to the rapid electronic spin‐lattice relaxation rate (&tgr;sl)−1of the Fe2+ion at elevated temperatures. However, this contribution has been observed at 77 K where the dependence of 1/T1on x is virtually identical to that observed in the Mn‐Zn system. The temperature dependence of 1/T1in FexZn1−xF2exhibits a critical‐like divergence near the Ne´el temperature, for x above the percolation limit.