In this study we aimed to evaluate the protein expression of class I histone deacetylases (HDAC) in testicular germ cell tumours (GCT) and to analyse differences between the histological subtypes of testicular GCT. 325 testicular GCT were included in a tissue microarray with each histological subtype of the tumour being separately represented on this array. Expression of class I HDAC isoforms 1, 2 and 3 was assessed by immunohistochemistry. While HDAC2 and 3 were highly expressed in all histological subtypes of GCT, HDAC1 was almost consistently expressed at lower levels. We observed significant differences in the expression of the respective HDACs between seminoma and non-seminoma GCT tissue components. Interestingly, choriocarcinomas showed generally high expression values for all three class I HDAC isoforms. Relevant correlations with clinicopathological parameters could not be demonstrated. Contrasting published findings on other tumour entities, no immediate practical diagnostic or prognostic value for HDAC1-3 in GCT could be inferred. However, the high expression levels might still be indicative for a treatment response to HDAC inhibitors which ought to be evaluated in further studies.