While obesity has links to poor semen parameters and reduced fertility, the causative links between obesity and male infertility are unclear, particularly on a molecular level. We investigated how obesity impacts the human sperm proteome, to further understand any implications for fertility. Sperm protein lysates from 5 healthy weight (BMI < 25) or obese (BMI>30) men were FASP digested, analysed by LC-MS/MS and quantitatively compared by label free quantification. Findings were confirmed for representative proteins by immunofluorescence staining. 2034 proteins were confidently identified, with 24 significantly less abundant (fold change <0.5) and 3 significantly more abundant (fold change >1.5)in sperm of obese men. These proteins were involved in a range of biological processes, including oxidative stress (GSS, NDUFS2, JAGN1, USP14, ADH5), inflammation (SUGT1, LTA4H), translation (EIF3F, EIF4A2, CSNK1G1), DNA damage repair (UBEA4) and sperm function (NAPA, RNPEP, BANF2). These results suggest that oxidative stress and inflammation are closely tied to reproductive dysfunction in obese men. These processes likely impact protein translation and folding during spermatogenesis, leading to poor sperm function and subfertility. The observation of these changes in normozoospermic men further suggests that traditional clinical semen assessment fails to detect important biological changes in spermatozoa which may compromise fertility.