The 26-year-old Australian turned professional with the team in 2014 after coming through the Australian Jayco-AIS development set-up and will now take the association to a sixth and seventh year.
"I am very happy, I have been with the team now for five years and I think we have a good relationship together and I am learning a lot from what I am capable of doing and also what the team expects in the direction the team has been heading," said Howson.
"I am really happy of being a part of the development of the team and I hope to improve on that in the years to come. I've built a lot of friendships within the team with the staff and riders and I feel that the relationship between every rider is ultimately the importance of having a great team. We are all aiming to achieve our best and grow so over the next two years I am hoping to be a part of the many more successes I am expecting the team to have."
Howson won the Herald Sun Tour in 2017 but has found his feet working in the service of others.
Mitchelton-Scott have undergone a transformation into a Grand Tour-winning squad, and Howson is developing into an important domestique for the Yates twins and Esteban Chaves. He supported Chaves to podium finishes at the Giro d'Italia and Vuelta a España in 2016 - putting in a noteworthy shift to help unseat Alberto Contador on the final day of the Vuelta - and was part of the squad that won the recent Vuelta with Simon Yates. On top of that he has ridden the Tour de France in the past two seasons.
"Damien has been with the team since he turned professional, so we are really pleased to announce that he will be continuing his career with us. The relationship and development is really moving in the right direction," said the team's head directeur sportif, Matt White.
"The key for him is to continue to get experience in riding at the highest level including Grand Tours, learning from them and targeting the next goals we have for them. We are a team that is evolving and to have him with us on this journey is exciting for both parties.
"He didn't get to finish the Tour de France this year because of an injury so his appearance at the Vuelta was another good opportunity for him to do a three-week race and get more comfortable with his role. Being part of a winning Grand Tour team is something very special and I am sure he learnt a lot from the experience. Now onto our next challenges in 2019 and beyond."