The Commission is the policy engine. It proposes legislation, is responsible for administration, and ensures that the provisions of the treaties and the decisions of the institutions are properly implemented. It has investigative powers, and can take legal action against persons, companies, or member states that violate EU rules. It manages the budget and represents the Union in international trade negotiations.

The European Commission is composed by 20 Commissioners of which two are from France, Germany, Italy, Spain and the United Kingdom, and one for each of the other member states. They are appointed for five-year terms, in line with the European Parliament, which approves the appointment of the Commission as a body.

The Commission President is appointed by agreement among the member governments in consultation with the European Parliament for a term of five years. Up to two Vice-Presidents are appointed from among the Commissioners.

The Commissioners act in the Union's interest, independently of the national governments, which nominated them. Each is assigned one or more policy areas and is assisted by a small cabinet or team of aides.

The Commission's administrative staff, based mainly in Brussels includes more than 15,000 staff, divided among more than 30 "directorates-general" and other administrative services.