ABSTRACTTurf‐type tall fescue (Festuca arundinacea Schreb.) germplasm available both commercially and in cultivar trials is surprisingly similar in quality and performance. To test genetic diversity within this germplasm, Diversity Arrays Technology (DArT) was used to detect DNA polymorphism among 93 entries from the 2006 National Turfgrass Evaluation Program tall fescue test in Riverside, CA. Based on the analysis of 190 polymorphic DArT markers, we found little variability in the turf‐type cultivars. These data are in agreement with field observations showing very few distinguishable differences in turf quality among the entries, with the exception of ‘Kentucky‐31’, a forage‐type standard entry. This cultivar ranked lowest for turf quality. The 93 entries were then compared with 14 forage‐type and four turf‐type accessions collected worldwide, further demonstrating narrow diversity among the entries and overall lower genetic diversity among turf‐types relative to forage‐types. Such low genetic polymorphism of turf‐type genotypes indicates a very close relationship regardless of the origin. It may have been caused by either a severe genetic bottleneck in the conversion of germplasm from forage to turfgrass use, or by extensive sharing of germplasm. This indicates an urgent need to rapidly broaden the genetic diversity in commercial germplasm of turf‐type tall fescue.