Tuchel gave Pulisic his first team debut at Borussia Dortmund in 2016.
"I remember making my debut under him and it was a really exciting time," Pulisic told chelseafc.com.
"I was playing in the youth team at Dortmund and then I got the call to say I was going to go up and train with the first team, and be a full first team member. It was really exciting.
"I had to fight my way into that team because it was a very strong team, and being a young player I had to work extra hard.
"The manager trusted in me and most importantly gave me chances to play, so I am grateful for that. He definitely helped me as a young player and I only have good memories of that time. We had some success at Dortmund together, and it's been good to see him again and work with him once more."
On again working with Tuchel, Pulisic is happy.
"It's been good so far," Pulisic reports. "We've got a new outlook on things, we have had a really good win so it's been a positive start.
"It's been some crazy times recently and just to get a win left all the guys in the changing room really excited. We have had a lot of fun in training and there are smiles on faces which is good to see."