School-based health centers (SBHCs) have been suggested as potential medical homes, yet minimal attention has been paid to measuring their patient-centered medical home (PCMH) implementation. The purposes of this article were to (1) develop an index to measure PCMH attributes in SBHCs, (2) use the SBHC PCMH Index to compare PCMH capacity between PCMH certified and non-PCMH SBHCs, and (3) examine differences in index scores between SBHCs based in schools with and without adolescents. A total of six PCMH dimensions in the SBHC PCMH Index were identified through factor analysis. These dimensions were collapsed into two domains: care quality and comprehensive care. SBHCs recognized as PCMHs had higher scores on the index, both domains, and four dimensions. SBHCs based in schools with just young children and those with adolescents scored similarly on the overall index, but analysis of individual index items shows their strengths and weaknesses in PCMH implementation.