The purpose of the study was to investigate the effect of early ambulation after cardiac catheterization (CC) on patients' back pain, puncture site pain, vascular complications, urinary discomfort, general well-being perception and satisfaction level. This study was a randomized single-blinded controlled trial. Overall, 137 participants were randomly assigned to experimental (63 participants) or control (74 participants) group according to a computer generated random list. Early ambulation (ambulate at 4 hours post-CC) and routine post-procedure care of 12 to 24 hours were used in the experimental and control groups respectively. Independent t-test, Chi-square test, multiple logistic regression and generalized estimation equation model were applied to compare various outcomes between experimental and control groups. Only one patient in the control group experienced puncture site bleeding after CC. Ambulation at 4 hours after CC significantly reduced patients' back pain 8 hours after they returned to the unit (OR=0.19, 95% CI: 0.08-0.45, p<0.001) and in the next morning (OR=0.36, 95% CI: 0.15-0.87, p=0.023), decrease urinary discomfort (OR=0.35, 95% CI: 0.14-0.90, p=0.03 for "very or unbearable urination discomfort" and OR=0.22, 95% CI: 0.06-0.74, p=0.015 for "much difficulty or unable to urinate at all"), and increase general well- being (p=0.005 for vitality subscale and p=0.014 for the total general well-being). However, it made no significant differences on puncture site pain as well as the satisfaction level of patients. The study enhanced health providers' understanding about the effects of early ambulation on patient outcomes. Nurses may provide more individualized and appropriate care to post-CC patients in a more competent and cost-effective way.