Kusini Yengi scored twice as Pompey beat Burton at a rocking Fratton Park to maintain their fine League One form.
They had to be patient to wear down their stubborn opponents and Yengi missed a great chance before netting a cheeky penalty just before the break.
He doubled the advantage in the second half and the dominant Blues appeared to be cruising to victory.
But John Brayford reduced the Brewers’ deficit late on, leading to a few nervy moments before the points could be celebrated.
John Mousinho made three changes from the side that were held to a draw at Blackpool at the weekend.
Australia international Yengi was brought in to lead the line, as leading marksman Colby Bishop was afforded a rare rest.
The other two switches were enforced, with injuries to Jack Sparkes and Callum Lang seeing Owen Moxon and Christian Saydee enter the fold.
That necessitated a change of formation, as Joe Rafferty moved inside to form a back three with Sean Raggett and Conor Shaughnessy.
And there was the welcome sight of Lee Evans being named among the substitutes following his arrival at the start of the month.
The visitors almost took a shock lead in the very first minute, as a 25-yard rocket from Rekeem Harper left the crossbar rattling.
But Burton were mostly content to sit back with a solid back five and ensure Pompey could not break through them easily.
Abu Kamara thought he should have won a penalty after going down in the box under a challenge from former Fratton loanee Steve Seddon, but referee Adam Herczeg did not agree.
The hosts did come close to breaking the deadlock on 15 minutes, though, courtesy of a fierce Marlon Pack free-kick that struck the bar.
Saydee also sent a couple of dangerous ball into the mixer that the opposition defence did well to deal with.
With the Brewers getting so many men back, a set-piece seemed a likely route for the Blues getting on the scoresheet.
And Albion's tactics were clear when keeper Max Crocombe was booked for taking an age over a goal-kick.
Pompey came close from another free-kick midway through the first half, as Moxon’s attempt flew narrowly over.
But it was from an Albion corner that they should have finally forged ahead on 37 minutes, with a quick counter-attack launched.
Kamara surged forward and laid a pass off for Lane, whose low centre was somehow turned wide by Yengi with the goal gaping.
He did not seem to let the miss affect him, though, with the striker bursting through a couple of defenders before cutting the ball back.
It managed to evade everyone, but the move stayed alive and an eventual Pack drive was beaten away by Crocombe.
Burton seemed to have done enough to go in level at the break, only for Yengi to have the final say in stoppage-time.
He drew a clumsy challenge from Deji Oshilaja inside the area and Herczeg immediately pointed to the spot.
It was YENGI who dusted himself down to take the penalty, showing plenty of nerve to dink the ball straight down the middle.
Half Time: Pompey 1 Burton 0
Will Norris did not have much to do before the break, but was called into action immediately following the restart after Tom Hamer’s long throw had caused problems in a crowded box.
Pompey soon started to take control again, with Pack dictating play as he sprayed clever passes around.
But for all their dominance, the hosts were struggling to get many shots away with so many black-shirted players back behind the ball.
They had a great chance when Pack stole possession and cut the ball back into the box, but Myles Peart-Harris missed it and Kamara blazed over the bar.
Pompey were denied another penalty just before the hour mark when Peart-Harris appeared to get shoved to the turf by Hamer.
But a second goal did arrive soon after, when Moxon released Kamara on the right and his teasing low centre was fired into the roof of the net from close range by YENGI.
The hosts continued to look comfortable in possession and were passing the ball around nicely in search of more openings.
There was a welcome return to action for Zak Swanson on 79 minutes, with the defender replacing Kamara to make his first appearance since just before Christmas.
But Burton suddenly had a route back into the contest when the Blues failed to deal with Bobby Kamwa’s delivery and the ball dropped for Brayford to fire into the net.
The visitors then thought they should have been awarded a penalty for Swanson’s challenge on Kamwa, only for Herczeg to dismiss their appeals.
Mousinho made a double switch on 84 minutes, as Yengi and Peart-Harris made way for Bishop and Gavin Whyte.
And the Blues managed to see out the closing stages without too much trouble to maintain their healthy lead at the summit.
Pompey (3-4-2-1): Norris; Rafferty, Raggett, Shaughnessy; Kamara (Swanson 79), Moxon, Pack (c), Lane; Saydee, Peart-Harris (Whyte 84); Yengi (Bishop 84)
Goals: Yengi 45+3 (pen), 63
Booked: Peart-Harris
Subs not used: Macey, Towler, Evans, Martin
Burton (3-4-3): Crocombe; Hamer, Brayford (c), Sweeney; Caprice, Harper (Ola-Adebomi 61), Powell, Seddon (Kamwa 69); Oshilaja (Gilligan 61), Hugill (Hackford 69), Helm (Carayol 69)
Goals: Brayford 80
Booked: Helm, Brayford, Crocombe, Carayol, Sweeney
Subs not used: Blackman, Bola
Referee: Adam Herczeg
Attendance: 19,536 (97 away fans)
