After graduating from the Police Academy, he worked as a detective in various ranks in the Istanbul Homicide Bureau for about 9 years. He won the Prime Ministry Master's Scholarship and completed his master's degree on "Criminal Investigations and Technologies" at the John Jay College of Criminal Justice in New York, USA, and returned to his job in 2002 After his return, he worked as the Director of the Organised Crimes Branch of the Headquarters of the General Directorate of Security, where he established the "High Technology Crimes and Information Systems Centre", which is now the Department of Combating Cyber Crimes, and later became the Branch Manager of the Crime Scene Investigation and Identification Units of the Criminal Police Laboratories.
After 22 years in the police profession, Demirbilek retired in 2005 at the rank of Chief of Police and moved to the private sector. After working as the director of Departments such as Corporate Security, Fraud Risk, Information Security, Business Continuity, Emergency and Crisis Management and Internal Investigations of multinational companies such as Citigroup, Nestle and Vodafone for about 14 years, he founded My Security Analytics (MySA), the first company in the field of security analytics in both public and private sectors, in 2018 He is currently the General Manager of MySA and the Chairman of the Board of Directors of its subsidiaries FinalCheck and Securitma. Since 2021, he has been a member of the Board of Directors and Vice President of the Cyber Security Federation.
In addition to his professional work, he took part in numerous articles, TV programmes and academic studies on "Criminal Investigations, Corporate Investigations, Management of Harmful Risks and Fraud Prevention Methods". Since 2014, his detective interview and novel series named "Murder Conversations", "We Are All Murderers", KAVGAZ - Bagci and KAVGAZ - Pilot have taken their place on the shelves. Mesut Demirbilek, who is also a faculty member at Üsküdar University Institute of Addiction and Forensic Sciences, has active memberships in associations and organisations in various fields such as ACFE, USİUD (International Association of Fraud Investigation Specialists), FUTURE CRIMES, ASIS International, Information Security Association.