The incidence of young-onset colorectal cancer (YOCRC) is rising. This patient population often presents with advanced disease and is treated more aggressively, raising unique challenges—particularly regarding fertility and sexual function. This chapter explores the multifaceted impact of YOCRC treatment on fertility and the importance of early reproductive counseling. YOCRC patients frequently undergo multimodal therapy, including chemotherapy, radiation, and surgery—all of which can impair fertility. Chemotherapeutic agents like oxaliplatin and irinotecan are known to be gonadotoxic, with variable long-term effects in both men and women. Pelvic radiation carries high risks for both gonadal failure and uterine or testicular dysfunction. Surgical interventions can damage reproductive organs or alter anatomical and hormonal function, leading to infertility. Fertility preservation methods—including sperm or oocyte cryopreservation, embryo freezing, ovarian transposition, and tissue cryopreservation—offer patients the possibility of future biological parenthood but require early intervention. Additionally, sexual dysfunction is common, driven by nerve damage, radiation effects, anatomical changes, and psychological distress, all of which may further impair reproductive potential. Given that YOCRC patients are often first evaluated by surgeons, it is critical for providers to discuss fertility and sexual health early and refer patients to reproductive specialists. Improved provider awareness and proactive counseling can help preserve future family-building options and enhance quality of life for this growing patient population.