Background: Sexually Transmitted Infections (STIs) remain an important public health concern, particularly in resource-limited settings where syndromic management is widely used for diagnosis and treatment. The effectiveness of this approach depends substantially on the knowledge, skills and adherence of healthcare providers to established STI management protocols. Objective: To evaluate healthcare providers’ adherence to national STI treatment protocols in the diagnosis and management of STI cases at primary healthcare centers in Khartoum State, Sudan and to assess the influence of STI-related training and professional characteristics on management performance. Methods: A cross-sectional observational study was conducted over six months among healthcare providers working in selected primary healthcare centers in Khartoum State. A total of 56 healthcare providers were assessed using an observational checklist and a semi-structured questionnaire. The assessment covered history taking, clinical examination, diagnosis, patient counseling and education and adherence to treatment protocols. Descriptive statistics and chi-square tests were used to evaluate performance and associations between provider characteristics and STI management. A p-value of <0.05 was considered statistically significant. Results: Overall STI management performance was predominantly fair or poor, with only 5% of healthcare providers demonstrating good overall performance, while 57% were rated fair and 38% weak. Major deficiencies were observed in diagnosis, counseling, clinical examination and adherence  to  treatment  protocols.  Only 44%  of  providers  had  received  STI-specific  training.  Providers  who  had received STI-related training demonstrated significantly better management performance than those without training (p = 0.001), whereas the frequency of training was not significantly associated with performance (p = 0.40). Professional category was also significantly associated with performance (p = 0.04). Performance varied substantially across STI syndromes, with scrotal swelling showing the highest proportion of good performance (73%), while inguinal bubo had the poorest performance (3% good). Conclusion: STI case management among healthcare providers in primary healthcare centers in Khartoum State was generally suboptimal, with substantial gaps in diagnosis, counseling, clinical examination and adherence to treatment protocols. STI-related training was significantly associated with improved management performance, although repeated training alone did not demonstrate a significant effect. Targeted competency-based training, supportive supervision and strengthening of STI management practices are needed to improve the quality of STI care in primary healthcare settings.