Although patients with life-limiting illnesses have reported that expressions of love, gratitude, and forgiveness facilitate life completion, these expressions have not been systematically measured within the context of close, personal relationships and advanced cancer. This study evaluated the RelCom-S, a newly developed screening instrument that assesses which relationships are considered important (self, others, God/higher power); whether one has communicated expressions of love, gratitude, and forgiveness; and the importance assigned to each. Face-to-face interviews were conducted with 125 adult patients with advanced cancer. The RelCom-S consists of 7 item pairs. For each item, participants indicated whether it was important and had been completely addressed. Higher scores indicated more unresolved relational issues. Outcome measures included QUAL-E life completion subscale, IPRI (Tilden Interpersonal Relationship Inventory) relational conflict subscale, and Memorial Symptom Assessment Scale. Forty-eight percent of participants reported at least 1 unresolved relational expression; 26% reported more than 1. RelCom-S scores correlated positively with negative mood, interpersonal conflict, and psychological symptoms and negatively with life completion. Approximately 50% of participants reported some unaddressed relational expression on the RelCom-S. This simple, clinically useful screening instrument will help clinicians identify specific relational and communication needs of patients with advanced cancer that could inform comprehensive assessments with targeted, timely interventions.