An own-goal from Harrier's Tyrone Williams little over ten minutes from time gave the Magpies a hard-earned win on the road.
Both sides lost in the National League North play-offs, Chorley in the final, so on paper this looked like a vital game so early in the season.
Chorley manager Jansen knew the importance of the fixture and he told the club's website: "I'm very pleased, it was a tough game, it's a tough place to come. We put in a performance. We were in their faces, aggressive and we played when we could.
"They're a very good side, a full-time team and I think last season they only lost once at home and they won't lose many here this time. The boys put an unbelievable shift in and managed to come away with the three points which is very valuable.
"We had a game plan to try and frustrate them and play high. We didn't have long periods of play but that wasn't our plan. We got what we deserved in the end."