Background: Losing a loved one during the COVID-19 pandemic is a potentially traumatic loss that may result in symptoms of persistent complex bereavement disorder (PCBD), posttraumatic stress disorder (PTSD), and depression. To date, grief-specific cognitive-behavioural therapy (CBT) has mostly been delivered through individual face-to-face formats, while studies have shown that online treatment also yields promising results. Offering treatment online is now more than ever relevant during the pan demic and may offer important benefits compared with face-to-face CBT, such as lower costs and higher accessibility. Our expectation is that grief-specific online CBT is effective in reducing PCBD, PTSD, and depression symptoms.Objective: Our aim i...