Saints were flattered by the final score as they barely staggered into the top four of the final table to claim a bye in the first round of the Premiership next week.
It was only in the last few minutes of the game they made sure of beating a Paris side far more capable and committed than the one that lost 42- 4 at Knowsley Road in the World Club Championship play-off last month.
Indeed, if Paris had not ruined some decent work in the middle of the park with woeful handling when they moved the ball wide, they could have embarrassed Saints severely.
They were arguably the better of two error-prone sides in the first half, when two goals apiece and tries from Chris Joynt for Saints and Paul Evans for Paris cancelled each other out.
Where Saints won the match was in the third quarter, when two converted tries without reply put them in a tolerably comfortable position almost despite themselves.
Soon after the break, Karle Hammond's pass sent in Danny Arnold and then, after an hour, a crisp piece of distribution by Bobbie Goulding sent Paul Newlove charging in.
Paris, the main business of the season completed when they avoided relegation, came back into the match, but not with sufficient momentum.
"If we had taken the bull by the horns we would have won," insisted Andy Goodway, who has served his time in France and will today be confirmed as the new Great Britain coach.
As it was, Jason Martin's pass and Joe Taylor's drive for the line brought them back to within one score and there was still the vague possibility of them snatching a result until Keiron Cunningham swivelled in the tackle and found his way over the line for the clincher.
"We thought we just had to turn up" was St Helen's Shaun McRae's assessment of a lethargic display. "But after all the problems we have had this year, third place is a very, very good result."
McRae will now join forces with Goodway as the new coaching team for the national side to face his native Australia in November. Both men will be hoping for more from their side then than they got yesterday.
St Helens: Arnold; Stewart, Matautia, Newlove, Sullivan; Long, Goulding; Leathem, Cunningham, O'Neill, Joynt, McVey, Hammond. Substitutes used: Perelini, Pickavance, Northey, Cross.
Paris St-Germain: Bird; Mahony, Chamorin, Evans, Bergman; O'Connor, Martin; Priddle, O'Donnell, Cabestany, Peters, Hancock, Lomax. Substitutes used: Sing, Taylor, Bellamy.
Referee: R Connolly (Wigan).Reuse content