Few studies have examined how spiritual well-being changes over time in patients with heart failure. We conducted a secondary analysis of data from the Collaborative Care to Alleviate Symptoms and Adjust to Illness (CASA) trial (N = 314). Spiritual well-being was measured using the Functional Assessment of Chronic Illness Therapy-Spiritual Well-Being Scale (FACIT-Sp) at baseline and 12-month follow-up. Of the 165 patients with spiritual well-being data at follow-up, 65 (39%) experienced probable clinically meaningful changes (> 0.5 SD) in spiritual well-being (35 improved, 30 declined). Increased pain (p = 0.04), decreased dyspnea (p < 0.01), and increased life completion (p = 0.02) were associated with improvement in overall spiritual well-being. Exploratory analyses found different predictors for FACIT-Sp subscales.