While the association between maternal nutrition and female reproductive fitness and offspring health is well recognised, the role that paternal diet plays in shaping male reproductive health is relatively poorly understood. It is, however, well established that poor diet has adverse effects on sperm quality, which in turn have a negative impact on embryo development and offspring health. It is conceivable that behind any alterations to sperm quality, there are certain underlying changes in testicular morphology. Few studies, however, assess the impact of diet on testicular histology. Therefore, we fed C57BL6 male mice either a control normal protein diet (18% protein; NPD), isocaloric low protein diet (9% protein; LPD), or a low protein diet supplemented with methyl donors (MD-LPD) for at least 7 weeks. Testes were collected and processed for either morphological (histology) or gene expression (RT-qPCR) analysis. We observed that LPD-derived testes displayed significantly increased mean total seminiferous tubule area and epithelium relative to NPD and MD-LPD (P<.02). In contrast, increased tubule lumen area was observed in response to MD-LPD (P=.02). Analysis of gene expression patterns revealed that testicular expression of anti-apoptosis gene Bcl2 (Apoptosis regulator Bcl-2) was increased in response to LPD and MD-LPD (P<.05), whereas the expression of the pro-apoptosis gene Bax (Apoptosis regulator BAX) was significantly decreased in the MD-LPD group (P=.01). Finally, we assessed testicular apoptosis using TUNEL staining. We observed that the level of apoptosis was significantly decreased in LPD when compared to NPD (P=.014). In addition, the supplementation of LPD with certain vitamins and minerals mitigated some of the changes to testicular morphology and apoptosis. This data provides further insight into testicular morphology and apoptosis in response to poor paternal diet and the possible underlying mechanisms taking place.