The Ireland captain struck with three minutes remaining to send his side second in the Guinness Six Nations Championship table – but coach Andy Farrell admitted, the win “wasn’t for purists”.
Pundits laughed at the ‘chaos’ of the first half but in an action-packed, if technically untidy, match the visitors triumphed at the empty BT Murrayfield for the second consecutive match.
Scotland had hauled themselves level at 24-24 with five minutes to play but Ali Price’s late penalty concession gave Sexton another penalty chance – and he continued his prolific form witnessed all week by his coach.
Farrell revealed: “Johnny has been on fire with the boot in training and I don’t think he missed one yesterday or pre-match. You hope that will transfer into the game, and big players nail those big moments.
"We’ll certainly take a win by three points at a hard place to come with a good Scotland side.”
Scotland had battled back from 24-10 down to draw level and Farrell hailed his side’s attitude right to the end – despite conceding what Sexton later described as “soft tries unacceptable at international level”.
Farrell added: “To hold Scotland for so long, and then they get their try to draw the game, to have the composure and the reset mindset to go again and come up with a special play, blockage, turnover ball and then to kick the goal… it was messy at times it wasn’t for the purist
“Our set-piece was great an especially the line-out and defensive line-out was incredible. Credit to the lads for taking ownership there.
"It got scrappy and gave them access back into the game but the fight, the will and want for the shirt to cross the line at Murrayfield was incredible and we got there in the end.”
Man of the match Tadhg Beirne admitted he had his fingers crossed when Sexton lined up his kick with three minutes to go and the good fortune came in handy, Sexton later conceded.
He said: “It was tough here with a swirling wind but you pick your line and bang it up at the left post trying to keep it low. It got a little lucky to be honest – it wasn’t my best strike of the day but it got there.
“We are letting in soft tries that are not acceptable at international level. We dominated large parts of the game and were 14 points up but then suddenly we’re drawing. We showed great character to stay in the moment and bounce back.
"We have been working on our concentration and not conceding soft tries but to be fair to Scotland their last try was good play, they held the ball through a large number of phases and they’re a very good side.”
The penalty was enough to send Ireland second behind unbeaten Wales with England up next. Speaking to BBC Sport Sexton added: “If we can finish second after the start we had to this competition it’ll be a good result.”