It is the first time the vaccine has been authorised for people aged under 18.
The European Medicines Agency (EMA) has approved the use of Moderna's COVID-19 vaccine for children aged 12 to 17.
It is the first time the vaccine has been recommended for people under the age of 18.
The EU regulator said research in more than 3,700 children showed that the jab produced a comparable antibody response to adults.
Sore arms, headache, and fatigue were the most common side effects reported by young adults in the trials.
The jab, which had already been approved for adults in Europe, is just the second vaccine to be licensed for children in the European Union.
Until now, the vaccine made by Pfizer and German partner BioNTech has been the only option for children in Europe and North America.
"The use of the Spikevax vaccine in children from 12 to 17 years of age will be the same as in people aged 18 and above," the EMA said in a statement.
"It is given as two injections in the muscles of the upper arm, four weeks apart."
The US Food and Drug Administration is currently considering whether to extend the use of the Moderna vaccine to the same age group.
Although some EU countries have authorized Pfizer-BioNTech’s vaccine for children under 18, not all have decided to start using it, citing the minimal risks children face from the coronavirus.
Teenagers generally develop less severe forms of COVID-19 than older people, but they are not immune to infection.
European regulators have also cautioned that both MNRA vaccines developed by Moderna and Pfizer vaccines appear linked to extremely rare cases of chest pain and heart inflammation in young adults.
The EU regulator said it would continue to monitor the safety and efficacy of the Moderna vaccine in children as it is rolled out in member states.
Half of Europe's adults, or 200 million people, are currently vaccinated against COVID-19, the European Commission said on Thursday.