A truly miscible ternary miscible blend consisting of poly(epsilon-caprolactone) (PCL), poly(phenyl methacrylate), and poly(benzyl methacrylate) (PBzMA) was discovered. The three-polymer blend system was completely miscible within the entire composition range at ambient temperature up to about 150 degreesC, and ternary phase diagrams at increasing temperatures were characterized and interpreted. A ternary-interaction model based on the modified Flory-Huggins expression was used to describe the phase diagrams with the individual binary interaction strengths. The model fitted well with the experimental-phase diagram for the ternary blend system at T = 250degreesC, where the binary PCL-PBzMA blend system is on the critical points of phase separation. Interpretation of discrepancy between the model and experimental at other temperatures was handled with an empirical approach.