The death of a companion animal can cause severe grief, yet previous research investigating factors predicting grief has been hampered by limitations. We explored how attachment styles, continuing bonds, and time since loss interacted to predict grief severity in a large sample of individuals grieving the loss of a variety of companion animals. Participants (n = 496) aged between18 and 79 years (M = 41.60, SD = 13.62) who had lost a companion animal in the previous three years completed a continuing bonds questionnaire, and animal-oriented assessments of grief and attachment styles online. After controlling for time since loss, higher attachment anxiety predicted more severe grief, a relationship partially moderated by continuing bonds, whereas attachment avoidance predicted less severe grief irrespective of continuing bonds. We recommend reconsideration of the non-human animal exclusion in prolonged grief disorder, and suggest that bereavement supports embrace targeted approaches that consider attachment styles.