Objective: To determine the incidence, causative pathogens, risk factors, and clinical outcomes of early-onset sepsis (EOS) in very preterm (gestational age < 32 weeks) and very low birth weight (birth weight < 1500 g) neonates. Methods: This retrospective study analyzed data from the Thai Neonatal Network registry (2019–2024; total 22 neonatal units). EOS was defined as bacteremia or bacterial meningitis within 72 h of birth. Results: Among 792 neonates (median [interquartile range] gestational age, 28 [26–29] weeks; median [interquartile range] birth weight, 960 [779–1190] g), the incidence of EOS was 4.0% (n = 32). Predominant pathogens were Escherichia coli (n = 10) and Acinetobacter baumannii (n = 9). Antibiograms showed high non-susceptibility for E. coli and A. baumannii to gentamicin (44.4% and 83.3%, respectively) and cefotaxime (37.5% and 75.0%, respectively). Although E. coli remained susceptible to amikacin and meropenem (100%), A. baumannii exhibited extensive resistance (66.7% and 83.3%, respectively). Multivariable analysis identified chorioamnionitis (adjusted odds ratio [aOR] 1.12; 95% confidence interval [CI]: 1.07–1.18) and 5 min Apgar score < 7 (aOR 1.05; 95% CI: 1.02–1.18) as significant risk factors. EOS was independently associated with increased early neonatal mortality within 7 days of life (aOR, 1.26; 95% CI: 1.16–1.36). Conclusions: The incidence of EOS is high among very preterm infants in Thailand and significantly increases mortality rates. The prevalence of multidrug-resistant A. baumannii in neonatal EOS is a critical concern that limits the efficacy of empirical treatments. These findings highlight the urgent need for targeted interventions and enhanced antimicrobial stewardship to improve neonatal survival rates.