Male infertility is a growing global health concern, with declining sperm quality emerging as a major contributing factor. Sperm function and integrity are highly sensitive to a range of intrinsic and extrinsic influences. Environmental exposures such as heat, radiation, heavy metals, and endocrine-disrupting chemicals can impair spermatogenesis and sperm function. Lifestyle-related factors, including poor diet, smoking, alcohol consumption, obesity, and psychological stress, further exacerbate sperm damage through mechanisms such as oxidative stress, hormonal imbalance, and DNA fragmentation. Additionally, the increasing biomedical and industrial use of nanoparticles has raised concerns regarding their potential reproductive toxicity, as they can cross biological barriers and disrupt testicular physiology. In contrast, medicinal plants and their bioactive phytochemicals have shown promising protective effects in restoring sperm quality by mitigating oxidative stress, enhancing antioxidant defence, regulating hormonal activity, and improving spermatogenesis. This review synthesizes current evidence on how environmental and lifestyle factors, as well as nanoparticle exposure, compromise male reproductive health, while also highlighting the therapeutic potential of medicinal plants in preserving and enhancing sperm quality.