Background Blood is essential for saving lives, particularly in emergencies. However, many patients, especially in developing countries face delays in accessing safe blood due to inadequate infrastructure, insufficient blood banks, poorly equipped laboratories, unreliable transportation systems, low donation rates driven by cultural beliefs, fear, and misconceptions, poor blood donor recruitment and retention, economic constraints, and a general lack of awareness and education about blood donation. Ensuring safe transfusions requires advanced technology and promoting healthy, voluntary donations. Donor selection is crucial for safety, preventing adverse reactions through proper criteria and infection screenings. Donor deferrals can discourage donors and hinder recruitment, so identifying and addressing deferral causes is vital. Blood centers must balance quality and quantity by using thorough donor assessments. Efforts should focus on both recruiting new donors and retaining deferred ones to ensure a stable blood supply. Aim The aim of the study is to evaluate and analyze the patterns and causes of blood donor deferrals in a tertiary care hospital. The objectives are to determine the incidence and reasons for blood donor deferrals. Materials and methods A cross-sectional retrospective study was conducted for 36 months fromMay 2021 to May 2024.A simple random sampling method was used to select the blood donors who reported for donation. Data was obtained from records maintained by the blood center. Descriptive statistics were utilized to summarize the demographics of the blood donors, including deferral rates among males and females, and the frequency of temporary and permanent deferrals. A Chi-square test was done to find the association between gender and deferral rates in blood donation. This analysis aimed to explore gender variations and underlying health status differences between male and female donors, as these can influence deferral rates. Results From May 2021 to May 2024, 17,082 people registered to donate blood at the Blood Centre, Department of Transfusion Medicine. Out of these, 1,000 donors, or 5.85%, were deferred. The majority of donors were males 16,638, with only 444 females. Most deferrals (76.4%) were temporary, often due to low hemoglobin levels or recent alcohol intake. Permanent deferrals (23.6%) were usually due to uncontrolled hypertension and diabetes. A significant association was found between gender and type of deferral among participants (p < 0.05). Conclusion This cross-sectional retrospective study on blood donor deferral patterns in a tertiary care hospital highlights key reasons such as low hemoglobin, recent alcohol intake, hypertension, and diabetes. To improve donor eligibility and retention, targeted strategies including enhanced education and community engagement are essential. These efforts will strengthen blood transfusion services and support critical healthcare needs effectively.