Nacewa was the star of the show in their 15-10 victory at Parc y Scarlets as his right boot contributed every point for Leinster.
The Fijian slotted five penalties while Scarlets winger Lee Williams crossed for the only score of the game to make it a nervy final quarter.
But after defeat last time out against Glasgow Nacewa and his Leinster teammates were in no mood to let victory slip through their grasp for the second week in a row.
And the 29-year-old Nacewa, who turned down the chance to represent Fiji at the World Cup in order to help out Leinster in the early stages of the season, could not hide his delight after the win.
"That was a case of job done for us against a very good Scarlets side," he said. "We were desperate to get the win after last week and in the end it's a great result for us.
"It may not have been all that exciting but the win is by far the most important thing and we are delighted to have got that.
"We were really poor last week so we needed to turn it around and move forward and we have done that.
"I gave my word to Leinster that I would stay and help them out in the league and I'm happy with my decision, no regrets whatsoever and we need to push on now after this result."
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