Family caregivers of dying cancer patients may suffer from grief experiences and bereavement complications. Previous studies have proposed some psycho-emotional interventions for the management of these complications. However, little attention has been given to family-based dignity intervention and expressive writing. This study was conducted to examine the effects of family-based dignity intervention and expressive writing, combined and alone, on anticipatory grief in family caregivers of dying cancer patients. This was a randomized controlled trial, in which 200 family caregivers of dying cancer patients were randomly assigned to the 4 intervention groups: family-based dignity intervention (n = 50), expressive writing intervention (n = 50), combined family-based single dignity intervention and expressive writing (n = 50), and control group (n = 50). At baseline, 1 week and 2 weeks after the interventions, anticipatory grief was assessed by a 13-item anticipatory grief scale (AGS). We found a significant reducing effect of family-based dignity intervention on AGS (-8.12 ± 1.53 vs. -1.57 ± 1.52, P = 0.01) and its subscales including behavioral (-5.92 ± 0.97 vs. -2.17 ± 0.96, P = 0.04) and emotional (-2.38 ± 0.78 vs. 0.68 ± 0.77, P = 0.03) subscales compared with the control group. However, no significant effect was seen for expressive writing intervention and combined interventions of expressive writing and family-based dignity therapy. In conclusion, family-based dignity therapy may be a safe and low-cost intervention for relieving anticipatory grief among family caregivers of dying cancer patients. Additional clinical trials are needed to confirm our findings. Registration number: IRCT20210111050010N1.