This study compares the planetary boundary layer (PBL) height produced by the Goddard Earth Observing System-version 5 (GEOS-5) model with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Part of GEOS-5 is an Atmosphere Global Circulation Model (GCM) used by National Aeronautics and Space Administration. Model developers are uncertain of the precision of model PBL height predictions since verification by direct observations of the PBL height is sparse. Validation of the PBL height serves as a diagnostic on whether the physics and dynamics packages are correct in the model. In this work, we report the global daytime PBL heights derived from dissertation work by Jordan (2009). We believe that this is the first large-scale observational study of PBL heights using CALIPSO. In this paper, we compare CALIPSO PBL heights to matched PBL heights from the GEOS-5 Modern Era Reanalysis for Research and Applications (MERRA) model. Extensive comparisons between the model output and satellite observations in the Western Hemisphere and over Africa gave model-measurement correlation coefficients (R) of 0.47–0.73. Comparisons have been performed for regions over land and water using clouds, aerosols, and mixed cloud-aerosol features to detect the PBL. The present study provides insight of regional PBL height variances in the GEOS-5 model. For much of the study region GEOS-5 predicts PBL heights within 25% of CALIPSO observations. A case over the Equatorial Pacific indicates that the GEOS-5/CALIPSO PBL height ratios exceed 1.25. PBL height biases in the Equatorial Pacific may be related to the GCM coupling scheme implemented in GEOS-5. Also, in some regions, the CALIPSO PBL heights are generally higher than the GEOS-5 model.