Idiopathic oligoathenoteratozoospermia (iOAT) is a common finding in the evaluation of male infertility. Oxidative stress (OS) may underlie its pathology. Tamoxifen and L-carnitine are used to treat idiopathic male infertility. The aim of this work was to detect the efficacy of tamoxifen and L-carnitine on sperm parameters, sperm ultrastructure and seminal OS in iOAT patients. Sixty patients were recruited for this study and divided into three groups; the 1st was treated with tamoxifen, 2nd with L-carnitine and 3rd with both drugs. Semen analysis, malondialdehye (MDA) level and transmission electron microscopy were performed before and after three months treatment. The first group showed significant improvement in MDA levels, sperm concentration, sperm morphology, ultrastructural head, acrosomal and mitochondrial anoma- lies (P < 0.01). Other parameters were not significantly improved. In the 2nd group, significant improvements in MDA, sperm motility, sperm morphology, ultrastructural mitochondrial and tail anomalies were detected (P < 0.01). No significant improvement in the other parameters. Third group showed improvement in MDA, all semen parameters and all ultrastructural anomalies (P < 0.01). In conclusion, tamoxifen and L-carnitine are effective in improving seminal OS, semen parameters and sperm ultrastructure. Combination of both drugs is superior to monotherapy.