Sexually transmitted infections (STIs) represent a significant global health challenge, particularly among youth, due to their high prevalence and associated complications. Despite global efforts, limited knowledge and stigma continue to hinder prevention and control. This study assesses the knowledge and attitudes of students in medical and non-medical colleges at Baghdad University regarding STIs, highlighting gaps to inform targeted interventions. A descriptive cross-sectional study was conducted between November 2023 and June 2024, involving 510 students from five colleges at Baghdad University. A structured questionnaire assessed sociodemographics, STI knowledge, and attitudes. Knowledge levels were classified as high, moderate, or low, while attitudes were categorized as positive, neutral, or negative. Data were analyzed using SPSS version 26, with chi-square tests applied for statistical significance (p < 0.05). Among the participants, 78% demonstrated low knowledge of STIs, with significantly higher deficiencies among non-medical students (87.1%) compared to medical students (68.6%). Negative attitudes were prevalent (84.1%), with positive attitudes recorded in only 0.4%. Males exhibited better knowledge scores but comparable negative attitudes to females. Conclusion: The study highlights critical gaps in STI knowledge and attitudes, especially among non-medical students. Targeted educational interventions are needed to address these issues and improve awareness and prevention strategies.