SARS-CoV-2 variant B.1.1.7, first detected in September 2020 in the United Kingdom of Great Britain and Northern Ireland, has spread quickly to many countries around the world. While some publications have described the clinical features of adult patients with the B.1.1.7 variant, little information is available on newborn patients. We report the clinical characteristics, treatment and care practices for a 21-day-old newborn patient who was confirmed to be infected with SARS-CoV-2 variant B.1.1.7 in Viet Nam during contact tracing after her father was confirmed to be infected with SARS-CoV-2. The patient displayed no symptoms of COVID-19 on admission but 3 days later developed diarrhoea, vomiting, a runny nose and a productive cough. These symptoms lasted for 3 days before becoming milder for 1 day and then stopping until discharge. During treatment, the patient received Vietnamese traditional herbal peppermint extracts for cough and digestive probiotics for diarrhoeal symptoms. A saltwater solution (Sterimar 0.9%) was used to clean the patient’s sinuses. The patient was cared for and fed breastmilk by her mother, who was provided with personal protective equipment, including sterilized infant equipment, medical masks and hand sanitizer, during hospitalization. The patient’s mother tested negative for SARS-CoV-2 throughout hospitalization. In conclusion, we found no severely abnormal clinical symptoms in a newborn infected with SARS-CoV-2 variant B.1.1.7 during treatment. Our case suggests that newborn patients with the B.1.1.7 variant can receive exclusive breastmilk feeding if sufficient preventive measures are provided for both mother and child.