Most of men with non-mosaic Klinefelter syndrome (KS) are azoospermic and for many decades use of donor semen was the only possible way of becoming a father for KS men. In the last 20 years, hundreds of non-mosaic azoospermic KS men have been submitted to testicular sperm extraction (TESE) and an overall sperm retrieval rate (SRR) of approximately 40% per TESE cycle has been recently reported. Data about pregnancy rate and live birth rate after intracytoplamic sperm injection (ICSI) support now the notion that KS men should not be considered anymore infertile. SSR appears to be independent of surgical procedure (TESE or micro-TESE) and patient age, suggesting that the focal spermatogenesis in KS testes does not undergo a progressive seminiferous tubule hyalinization. Undefined yet is whether it is necessary to perform TESE before initiating testosterone therapy in hypogonadal KS men, or whether it is safe to wait until paternity is wished by interruption of testosterone treatment. TESE technique holds a risk for inducing or aggravating androgen deficiency in KS, independently of the surgical technique, indicating the need of endocrine monitoring after TESE to initiate testosterone treatment if needed. Of note, although TESE-ICSI gives the chance for an eventually normal live birth in non-mosaic KS men, it should be considered that the cumulative delivery rates per patient submitted to TESE is approximately 16% or lower. Prior to undergoing TESE, patients should be counseled that the majority of them will probably not father a genetically proper child.