Background: The typical history of acute appendicitis is observed in less than 60% of cases. Therefore, searching for a surrogate marker is mandatory. Our goal was to determine whether the soluble triggering receptor expressed on myeloid cells (sTREM-1) is an efficient biomarker for acute appendicitis. Methods: sTREM-1 serum levels were measured in addition to carrying out routine diagnostic tests (urine dipstick, complete blood count and CRP) in children admitted to the Emergency Department with suspected appendicitis. Statistical analysis was performed in order to examine whether sTREM-1 was a significant predictor of appendicitis. Results: Fifty three of 134 children enrolled in the study were diagnosed with appendicitis. There was no significant difference in serum sTREM-1 levels (p = 0.111) between children with or without appendicitis (n = 81). Leukocytes, neutrophils and CRP were significantly elevated in the appendicitis group (p < 0.001). The appendix diameter was significantly larger and the Alvarado score significantly higher in the appendicitis group (p < 0.001). Conclusion: serum sTREM-1 is not a good marker for acute appendicitis. Customary tests in addition to a proper patient history and physical examination are still the most effective methods to diagnose acute appendicitis.