The adverse effects of cigarette smoke cause almost all semen parameters (sperm count, motility and morphology) to deviate from normal physiological levels. It has been reported that there is no “safe” dose of cigarette smoke inhalation for sperm quality and that certain semen parameters, such as semen volume, are significantly and negatively correlated with smoking volume. Nicotine, an alkaloid extracted from the Solanum genus, has a detrimental effect on sperm morphology and number (because human sperm have nicotine receptors) and is present in higher concentrations in smokers. In rat animal experiments, nicotine had a dose-dependent adverse effect on semen parameters, reducing fertility in rats, and this effect was attenuated by removal of nicotine, suggesting a causal relationship between nicotine and decreased semen quality. Numerous clinical studies have reported reduced sperm counts and significant decreases in sperm concentration in smokers. These studies have found that smokers are prone to spermopenia and even sperm deficiency, which reduces or even lacks sperm with the ability to fertilize, leading to infertility problems, and studies have found that smokers’ sperm have reduced motility and reduced sperm quality compared to nonsmokers’ sperm. Specifically, smokers’ sperm showed weaker motility, more pronounced deviations in straight-line motion, and faster liquefaction after ejaculation. Finally, smokers’ semen contains more morphologically abnormal sperm, and these morphological changes include oval-shaped sperm, sperm head defects, and small cytoplasmic droplets compared to normal sperm. Thus, heavy smoking can lead not only to oligospermia and aberrant motile spermatozoa, but also to azoospermia in severe cases.