Inclusion Criteria:  community-dwelling adults (age 18 or over) who are currently taking the primary responsibility for the care of a relative with dementia living in the community having at least mild symptoms of psychological distress as measured by the Depression, Anxiety and Stress Scale (DASS-21;Antony et al., 1988) having a computer or a smartphone with the internet access at home and being able to provide informed consent  Exclusion Criteria:  having cognitive, physical, or sensory deficits or language barriers (non-English communicator) that impede study participation currently receiving a psychological therapy having a prior experience in ACT having psychiatric hospitalizations or diagnoses of mental illness in the previous two years taking antipsychotic or anticonvulsant medication at the time of recruitment considering or planning to place family members of PwD in a nursing home within 6 months or having the possibility of study dropouts due to medical conditions of caregivers (e.g., surgery that may affect mental health) and their relatives with dementia (e.g., conditions that may impede study participation due to frequent hospitalization or death)