From 2004 to 2007 he was serving as an Ambassador, Permanent Representative to the Organization for Security and Co-operation in Europe (OSCE), the United Nations Office on Drugs and Crime (UNODC), the International Atomic Energy Agency (IAEA), the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), the Nuclear Suppliers Group (NSG), the Wassenaar Arrangement (WA) and other international organizations in Vienna.

Next, from 2008 to 2013, he was the Head of NATO Weapons of Mass Destruction Non-proliferation Centre (WMDC) in Brussels.

He was responsible, among others, for co-chairing NATO-Russia Council's Working Group on Arms Control, Disarmament and Non-proliferation.

[4] In 2012, he joined the European External Action Service and was appointed the Principal Adviser and Special Envoy for Non-proliferation and Disarmament.

[7] Besides Polish, Bylica speaks English, Chinese, Russian and has working knowledge of French.