Introduction: Asthma is a prevalent respiratory condition, and biologic agents have proven effective in managing moderate to severe asthma. However, the role of biomarkers in guiding the use of biologic agents remains unclear. Method: On July 30, 2024, a systematic review and subsequent meta-analysis were conducted by searching three major online databases: PubMed, Web of Science, and Cochrane. Results: The final analysis included 10 studies with a total of 6,709 patients with moderate to severe asthma. The overall pooled effect across all ages demonstrated a rate ratio (RR) reduction of 0.61 (95% CI: 0.46 to 0.80; p < 0.01; I² = 71%). Subgroup analysis revealed an onset or treated age of less than 18 years with RRs of 0.79 (95% CI: 0.62 to 1.02; p = 0.07; I² = 0%) and 0.88 (95% CI: 0.42 to 1.84; p = 0.73; I² = 14%), respectively. Patients with varying blood eosinophil levels showed a pooled RR of 0.51 (95% CI: 0.38 to 0.69; p < 0.01; I² = 82.7%). However, blood eosinophil levels below 150/μL demonstrated a limited effect of biologic agents, with an RR of 0.77 (95% CI: 0.35 to 1.67; p = 0.50; I² = 87%). For patients with all levels of fraction of exhaled nitric oxide (FeNO), the RR was 0.43 (95% CI: 0.30 to 0.62; p < 0.01; I² = 84%). The test for subgroup differences yielded a p-value of < 0.001, indicating that patients with higher FeNO levels experienced a more significant reduction in RR. Conclusion: Patients with asthma onset or treatment before age 18 may benefit less from biologics. Blood eosinophil counts and FeNO levels aid in selecting these therapies.