Hartley made his first appearance for more than a month as he skippered Mallinder’s men at the Madejski Stadium on Boxing Day.
And the 29-year-old, who has been touted as favourite for the England capataincy under new boss Eddie Jones, was on the field for 61 minutes before being replaced.
Hartley had been suffering from concussion after sustaining a blow to the head in the defeat to Saracens on November 7.
But he is now back to full fitness and Mallinder was pleased to have the experienced forward back.
“Dylan went pretty well,” said the Saints director of rugby.
“It was always going to be tough, being out for a number of weeks and then coming back.
“He’s not trained that much with us but I thought he did pretty well on his first game back.
And he added: “Concussion’s a serious part of the game now and we are treating them seriously.
“It was just a question of time for Dylan and making sure he was 100 per cent right.”