Background: Little is known about the impact that having a family caregiver (FCG) has on individuals with advanced cancer. We examined patient characteristics and outcomes most associated with having versus not having a primary FCG. Methods: Secondary data analysis of a randomized controlled trial of an early palliative care intervention (Project ENABLE [Educate, Nuture, Advise, Before Life Ends]) for patients with advanced cancer and their primary FCGs (10/2010-9/2013). Sociodemographic and patient reported outcomes data were abstracted from the baseline questionnaires of 122 patients who enrolled with FCG and 85 patients who enrolled without a FCG. Sociodemographic variables included age, gender, education, race, social support (MSPSS: Multidimensional Scale of Perceived Social Support, score range: 12-84), and Karnofsky Functional status. Patient reported outcomes included symptom impact (QUAL-E Symptom Impact, score range: 4-20), quality of life (QOL) (Functional Assessment of Chronic Illness Therapy-Palliative Care, score range: 0-184), depression (Center for Epidemiological Studies-Depression Scale, score range: 0-60), perceived quality of care (Patient Assessment of Chronic Illness Care, score range: 20-100), and hospital days and emergency department visits in the past 3 months. Structured tree analysis was used to identify a set of variables strongly associated with the presence or lack of a FCG. Results: In the final model, for patients with MSPSS scores <52.5 (N=12), none had a FCG. For male patients with MSPSS scores >52.5 (N=105), 73% (N=77) had a FCG. For female patients with MSPSS scores >77.5 (N=29), 69% (N=20) had a FCG. For female patients with MSPSS scores <77.5 and QOL scores >126.1 (N=25), 20% (N=5) had a FCG. For female patients with MSPSS scores <77.5, QOL scores <126, and depression scores >26 (N=10), 20% (N=2) had a FCG. For female patients with MSPSS scores <77.5, QOL scores <126, and depression scores <26 (N=26), 77% (N=20) had a FCG. Conclusions: The final model suggests that having a FCG is highly associated with having high levels of perceived social support, being male, and lower levels of depression despite having lower QOL.