This study assessed the effects of incorporating Ulva lactuca methanolic extract (ULME) into a semen extender on the mitigation of cryodamage in ram sperm, including sperm kinematic parameters, acrosome integrity, redox balance, apoptosis-like changes, culturable bacterial counts, and ultrastructural preservation. Semen samples were collected using the artificial vagina technique from five fertile rams aged 12 to 14 months. The collected semen was cryopreserved in a tris-based extender supplemented with different concentrations of ULME: 0 mg/mL (ULME0), 0.25 mg/mL (ULME0.25), 0.50 mg/mL (ULME0.50), 1 mg/mL (ULME1), and 2 mg/mL (ULME2). The inclusion of ULME at concentrations of 1 and 2 mg/mL significantly mitigated cryoinjury, as evidenced by improved preservation of post-thaw sperm motility, viability, membrane integrity, and acrosome structure compared to the control group (p < 0.05), rather than enhancing these parameters beyond baseline levels. Moreover, these concentrations increased total antioxidant capacity and reduced malondialdehyde levels in the semen extender compared to the control group (p < 0.05). Supplementation with ULME significantly increased the count of viable sperm while reducing the number of apoptotic and necrotic sperm (p < 0.05). The total and coliform bacterial counts were notably lower in the ULME1 and ULME2-treated groups. Electron microscopy examination revealed that the addition of ULME to the cryopreservation medium preserved the integrity of the acrosome and plasma membrane, as well as the overall structural integrity of cryopreserved ram spermatozoa. Overall, ULME at 1 and 2 mg/mL may improve post-thaw sperm quality and reduce bacterial counts, although its effects on reproductive outcomes require further investigation.