Interest in internet-based interventions has increased considerably. The effectiveness of these applications continues to be investigated for the treatment of Prolonged Grief Disorder. This study includes preliminary findings of the internet-based and therapist-supported prolonged grief intervention program developed in Turkish. The internet-based program consists of 10 written sessions, and after each session the participants receive written feedback from the therapist. The program takes approximately 6-8 weeks. The preliminary findings of the program were handled in a proof-of-concept study style based on a case series design. Self-report measures were taken from the first eight participants who completed the program at four different times (pre-test, post-test, 1st and 3rd month follow-ups). In addition, the written contents of the first and last sessions were analyzed by content analysis. As a result of the descriptive findings, remarkable decreases were observed in traumatic grief, global meaning violation, depressive symptoms, and stress levels in a significant part of the participants between pre-post and follow-up measurements. Also, five of the participants had considerable increases in meaning reconstruction scores. In addition, the results of the content analysis indicated that following the intervention, the bereaved individuals expressed less negative and more positive content, as expected. These two data show that the intervention program is promising in reducing the symptoms of Prolonged Grief Disorder in bereaved individuals and may yield good results with controlled designs for a broader range of participants.