Hartley did not play any pre-season games after receiving an 11-week ban for his red card in last season's Aviva Premiership final, when he was found guilty of verbally abusing referee Wayne Barnes.
Some redemption came quickly for the England hooker when he scored Northampton's first of five tries after just two minutes and he was given a huge ovation when he was replaced in the 58th minute.
And Mallinder, who had to talk Hartley into retaining the captaincy after a summer of soul-searching for the hooker, was delighted with his display, that even saw him shake hands with referee JP Doyle and the fourth official when he came off.
Mallinder said: "I thought he was magnificent today. Dylan put in a determined performance today. There has been a lot of talk about him after what happened, but all he can do is play and show what he can do on the field.
"At half-time when we looked at the stats it showed he had covered the most metres in our team.
"He has worked very hard during the summer, he has had no pre-season games, so to come in and play like that shows what sort of player he is. He is our leader because he plays and leads by example."
Current England skipper Tom Wood also got his name on the scoresheet as Northampton ran riot in the first half with the Pisi brothers George and Ken and Sam Manu also scoring. British Lion George North missed out on his debut, but Mallinder is not fretting.
Mallinder added: "He is a magnificent player, he would love to have scored today, but I am sure that will come, he is so big and strong.
"I didn't really buy George to get people out of their seats, I brought him here to win games, and he did. If in the meantime people get people off the seats watching him then that is great as well."
Exeter head coach Rob Baxter added: "In the first half it felt like we were going through the motions, and the reality is you have to do a lot more than that against a top side.
"You have to have flat out commitment and that wasn't there in the first half.
"What I have got to do is find out why we were off the pace at the start of the game and how to get us firing again."