The hierarchical approach for specifying design inputs is a key feature of the new "Mechanistic–Empirical Pavement Design Guide" (MEPDG). The three levels of design input for the strength and stiffness characterization of portland cement concrete (PCC) range from a Level 1 laboratory measurement of modulus of elasticity and modulus of rupture at 7, 14, 28, and 90 days to a Level 3 estimation of the 28-day unconfined compressive strength. This paper evaluates the effect of design input level for PCC strength and stiffness properties on MEPDG performance predictions for jointed plain concrete pavements (JPCPs). The effects of the different PCC stiffness and strength design input levels on predicted faulting, transverse cracking, and international roughness index (IRI) are evaluated for eight PCC mixtures in several JPCP design scenarios. Faulting was found to be insensitive to the MEPDG PCC input level, transverse cracking was extremely sensitive, and IRI was only moderately sensitive. In particular, the results showed that the Level 3 input combination of a measured 28-day modulus of rupture and a measured 28-day modulus of elasticity yielded predicted distresses that were consistently in closest agreement with predictions that used Level 1 inputs. Reliable and accurate 28-day modulus of rupture and modulus of elasticity values can therefore be used as less-expensive and more-practical alternatives to full Level 1 stiffness and strength characterization in JPCP analysis and design. When full Level 1 characterization is performed, high-quality testing is mandatory for avoiding small anomalies in measured values that can cause physically unrealistic predictions by the MEPDG of stiffness and strength gains over time.