De Waele started his career in 1981 with the then gendarmerie. He worked there, among other things, at the murder section and conducted the investigation into the kidnapping of Anthony De Clerck.
De Waele was known to the general public as head of the Pedophilia cell of the Brussels federal judicial police. That cell was set up just before the outbreak of the Dutroux case in 1996. In 2011, he wrote the book ‘Can you keep a secret?’ about his experiences as a pedophile detective. In it he gave, among other things, practical prevention tips for parents.
After the attacks in Paris in November 2015, De Waele called on the media and Twitter users not to communicate about the locations where house searches took place during a police action in Brussels. As a result, Twitter users began posting images of cats en masse. The police thanked them a day later with a striking tweet.
In 2018, Catherine De Bolle became head of Europol in The Hague. Peter De Waele moved with them and became a communication advisor for De Bolle.