The global trend on (male)infertility is concerning and the unidentifiable causes in half of the cases demands a better understanding of the molecular, biochemical and metabolic mechanisms as well as the identification of external and internal factors operating behind it, that might help to explain this apparently unjustified infertility. This can only be achieved through a comprehensive analysis of the infertile men, in which external (lifestyle, occupational and environmental factors) and internal factors (psychological distress) should also be evaluated and considered, but also assessing sperm function beyond the routine seminal analysis. In this prospective cohort study, 79 sperm samples, from men who were male partners in couples seeking for infertility treatment, were collected at the Reproductive Medicine Unit (CHUC) from July 2018 to July 2022 and analyzed by SWATH-MS. Based on couples’ clinical data, seminal/hormonal analysis, and strict exclusion criteria, samples were categorized in the different groups, namely control (CTRL; 50 individuals), idiopathic infertile (ID; 19 patients) and unexplained infertile (UMI; 10 patients) men. In general, ID patients presented the worst sperm functional profile, while the UMI patients were observed to be similar to controls. These differences were also observed at the proteomics levels, which revealed 145 differentially expressed proteins (DEP) between the three groups, with more than 120 proteins being altered between ID and the other groups, and only 14 proteins were considered altered between CTRL and UMI.