Background: In the last decades, a substantial decline in sperm counts has been described. We aim to evaluate clinical outcomes of treatment strategies in patients referred to andrology due to abnormal sperm parameters. Materials and methods: Observational descriptive study performed at one country's largest public reproductive unit during 5 years (2015–2019). Patients were selected according to the World Health Organization (WHO) criteria for sperm analysis. Results: A total of 670 patients were included, with a median age of 35 (18–54) years old. During the infertility investigation, 15 patients were diagnosed with Klinefelter syndrome and two with a disorder of sexual development (46, XX). Three malignant testicular tumors were identified. Among treatments applied—varicocele correction was the most frequent (31.49%, n = 210), followed by antioxidant therapy (11.04%, n = 74). Posttreatment sperm analysis was obtained in 255 cases, demonstrating an improvement in 58.04% (n = 148), including normalization in 6.67% (n = 17) of men. An assisted reproductive technique (ART) was performed in 45.97% (n = 308), with a clinical pregnancy rate per initiated cycle of 26.92% (n = 91). Among azoospermic patients (19.55%, n = 131), there was a higher exposure to heat (p = 0.02) and a higher prevalence of previous testicular surgery (p = 0.002), and orchitis (p = 0.022). Varicocele was more frequent in non-azoospermic patients (p = 0.007), while Y chromosome microdeletions and chromosomal alterations were mostly found in azoospermic patients (p = 0.004 and p < 0.001, respectively). Conclusion: Even in patients with a poor prognosis a priori, improvements in sperm parameters or sperm retrieval might be achieved after treatment, namely low-grade varicocele correction. Clinical significance: An adequate investigation of male infertility can improve reproductive outcomes and contribute to an early diagnosis/secondary prevention of tumors.