Saints started life under new boss Chris Boyd with a 26-13 win against Ospreys in torrid conditions at Brewery Field on Saturday afternoon.
Boyd, who arrived at Franklin's Gardens on Thursday, watched on as tries from Ollie Sleightholme, David Ribbans, James Fish and Api Ratuniyarawa proved enough to see off a determined home side.
Ospreys had gone 6-0 up through two early Sam Davies penalties and they did manage to score their first try from the final play of the game, with Matthew Aubrey dotting down.
But in between, Saints took a total grip of proceedings and they were able to bring new signings James Haskell and former Ospreys fly-half Dan Biggar, among others, off the bench in the comfortable success.
Saints were given a useful test and will return to Wales next Friday night, taking on the Dragons at Rodney Parade as pre-season preparations continue.
Ospreys had looked ready to upset Boyd's men when they took the lead in Bridgend, building on some good breakdown work to give Davies his first three points of the game.
The Ospreys forwards were clearly fired up and they won two quick scrum penalties, the first relieving pressure in their own 22 and the second giving Davies another chance to double the lead, which he took.
But Saints responded well and after lofty lock Ribbans pinched an Ospreys lineout, the away side produced a patient attack before some fast hands allowed wing Sleightholme to fly through, sidestep his man and score under the posts.
James Grayson converted to give the away side the lead for the first time and Saints were now starting to brim with confidence, playing some slick rugby despite the slippery conditions.
They kicked to the corner for another lineout and Ribbans pounced to pick up his side's second score of the day.
Grayson converted well to make it 14-6 and it was soon 21-6 as Saints again turned the screw from a lineout, with hooker Fish scoring and Grayson adding the extras again.
Four changes were made 12 minutes before the break, with summer recruits Haskell and Will Davis among the men introduced.
Saints held their 21-6 lead until half-time and, as expected, they made a raft of changes at the interval.
One of those was the introduction of Biggar, and his first act from the tee was to try to convert a Ratuniyarawa score.
But, to the amusement of a small section of home supporters, the Wales fly-half sent the kick wide of the posts.
That was all the home fans had to cheer about, and one shouted "come on, Ospreys - do something".
The Welsh outfit had struggled to get out of their own half but when they did eventually venture into Saints territory, the men in last season's striking lime away kit stood tall.
With changes continually being made on both sides, the game turned into a scrappy affair.
Conditions did little to help either side and it was largely left to the forwards to slug it out in a battle for ascendancy.
Saints more than held their own until the final seconds, when Ospreys put together a lineout drive and Aubrey scored.
James Hook added the extras, but it was to be a convincing victory for Boyd's men as the Kiwi boss started his time at Saints on a high note.
Ospreys: Moss; T Williams, Thomas, Allen, Morgan; S Davies, T Habberfield; R Jones, Otten (c), Botha; Ashley, Beard; W Jones, S Cross, Volpi.
Replacements: Phillips, Jeffries, Walsh, Nemsadze, Morris, Morgan-Williams, Evans, Hook, Lake, Aubrey, K Williams, Dirksen, D Cross, John, Ratti.
Saints: Emery (Collins 40); Sleightholme (Worley 40), Dingwall (Burrell 40), Hutchinson (Strachan 40), Pisi (Tuitavake (40); Grayson (Biggar 40), Reinach (Mitchell 28 (Tupai 60)); van Wyk (Davis 28 (Waller 60)), Fish (Gray 40), Franks (Painter 40); Barrow (Ratuniyarawa 28 (Onojaife 40)), Ribbans (Craig 40); Gibson (Ryan 40), Brüssow (Haskell 28 (Ludlam 54)), Eadie (Harrison 40).