Male factor is responsible for 40–50% of infertility cases, contributing equally as a female factor. Oxidative stress has now emerged as one of the major causes of unexplained male infertility, as it leads to increased risk of deoxyribonucleic acid (DNA) fragmentation, decreased sperm motility, concentration and abnormal morphology. Though a certain amount of reactive oxygen species (ROS) activity is essential for normal functioning of sperms, an excess lead to pathological effects on semen parameters, ultimately resulting in male sub-fertility or infertility. Furthermore, oxidative stress affected sperm cells with damaged DNA result in increased risk of birth defects, neuropsychiatric problems and cancers in off-springs of such fathers due to increased risk of de-novo mutations in the germline and post-fertilization. Hence, present review helps in highlighting the facts about ROS, their production, physiological functions and pathological effects on sperm dysfunction and DNA damage, leading to male infertility. The literature regarding male infertility and role of ROS was searched from various peer-reviewed printed and online articles indexed in PubMed, MEDLINE, SCOPUS, EMBASE, etc. and from various governmental organizations till Jan 2018.