<p>Background: Few studies have investigated the relationship of seminal L-Carnitine (LC) with male infertility associated with varicocele. The purpose of this prospective cross-sectional study was to assess seminal plasma LC levels in infertile oligoathenoteratozoospermic (OAT) men with varicocele.<br /> Methods: Overall, 86 men were investigated. They were divided into infertile OAT men with varicocele (n=45), infertile OAT men without varicocele (n=21), and fertile men (n=20) as a control group. According to WHO guidelines, these men were subjected to history taking, clinical examination, and semen analysis. Seminal LC levels were evaluated by the colorimetric method. Statistical comparisons were done using Kruskal-Wallis and Mann-Whitney U tests and correlations were verified by the Pearson test. P-value&lt;0.05 was set to be statistically significant.<br /> Results: The mean seminal plasma LC levels were significantly lower in infertile OAT men with varicocele (216.3&plusmn;57.1 <em>ng/ml</em>) compared to infertile OAT men without varicocele (252.9&plusmn;62.9 <em>ng/ml</em>, p=0.01), or fertile men (382.8&plusmn;63.6 <em>ng/ml</em>, p=0.001). Besides, the mean seminal plasma LC level exhibited statistically significant decreases in infertile OAT men of varicocele grade III compared to varicocele grade II cases, and in infertile OAT men with bilateral varicocele compared with unilateral varicocele cases. Collectively, there was a statistically significant positive correlation between seminal LC levels with sperm concentration, motility, and normal morphology.<br /> Conclusion: Seminal LC levels are expressively reduced in infertile OAT men with varicocele and are influenced by an increase in varicocele grade and laterality.</p>