The literature on neonates with SARS-CoV-2 is mainly concerned with perinatal cases, and scanty data are available about environmentally infected neonates. To fill knowledge gaps on the course and prognosis of neonatal cases, we analyzed 1-year data from the Turkish Neonatal Society in this prospective cohort study of neonates with postnatal transmission. Data from 44 neonatal intensive care units (NICUs), of neonates with positive RT-PCR results at days 5–28 of life, were extracted from the online registry system and analyzed. Of 176 cases, most were term infants with normal birth weight. Fever was the most common symptom (64.2%), followed by feeding intolerance (25.6%), and cough (21.6%). The median length of hospitalization was 9 days, with approximately one quarter of infants receiving some type of ventilatory support. Myocarditis (5.7%) was the most common complication during follow-up. Among the clinical findings, cough (odds ratio [OR]: 9.52, 95% confidence interval [CI]: 4.17–21.71), tachypnea (OR: 26.5, 95% CI: 9.59–73.19), and chest retractions (OR: 27.5, 95% CI: 5.96–126.96) were associated with more severe clinical disease. Also, there were significant differences in the C-reactive protein level, prothrombin time (PT), partial thromboplastin time, international normalized ratio, and days in the NICU (p = 0.002, p = 0.012, p = 0.034, p = 0.008, and p < 0.001, respectively) between patients with mild-moderate and severe-critical presentations. A PT above 14 s was a significant predictor of severe/critical cases, with a sensitivity of 64% and specificity of 73%. Conclusions: Our data showed that late-onset COVID-19 infection in neonates who need hospitalization can be severe, showing associations with high rates of ventilatory support and myocarditis. Cough, tachypnea, and retractions on admission suggest a severe disease course. Trial registration: ClinicalTrials.gov identifier: NCT04401540.What is Known:• Neonatal cases of COVID-19 infection are mainly reported as perinatal COVID-19 cases.• Neonates with perinatal transmission have a mild course and favorable prognosis.What is New:• Among symptomatic neonates with late-onset COVID-19 infection, fever was the most common symptom, and almost one quarter of hospitalized cases needed some type of respiratory support. Myocarditis was the most common complication.• The presence of cough, tachypnea, retractions, and a PT above 14 s were associated with an increased risk of severe COVID-19.