Browne was sent-off in the 38th minute for kicking out at Sam Morsy in retaliation for the Boro midfielder twice catching him with his arm as they tangled near the half-way line.
He was perhaps as much sinned against as being the sinner, Browne protesting long and loudly before heading to the dressing room.
North End trailed 1-0 at the time of the dismissal, Jordan Storey slicing an attempted clearance into his own net without a Boro player being near him.
Before the own goal the visitors had been the better side, Sepp van den Berg hitting the bar with a 20-yard show.
Storey saw a header blocked on the line soon after, Scott Sinclair putting the rebound into the net but seeing it flagged offside.
Browne's red card was followed by one for his manager at half-time, Alex Neil confronting referee Oliver Langford on the pitch and taking his protests too far.
North End never looked like getting back into the game with 10 men and Boro effectively wrapped-up the three points early in the second half when Marcus Tavernier scored from the rebound after Chuba Akpom's shot had come back off the bar.
Defeat only increased the pressure on Neil, this a ninth Championship defeat of 2021 - their form having been wretched since the turn of the year.
Maybe Browne's red card will see him cut some slack but this form needs turning round quickly, Saturday's home game with Luton Town taking on huge importance.
The opening quarter of an hour or so offered little clue as to the drama would follow later in the first half.
It was North End hitting the woodwork in the 20th minute which seemed to bring things to life, van den Berg's angled drive from outside the box striking the bar and bouncing over.
Middlesbrough took the lead in the most unfortunate circumstances from PNE's point of view, Yannick Bolaise's cross from the left seemingly offering no threat.
Storey swung his right boot at it to make a routine clearance with no Boro player around him, the ball slicing off his foot and flying past Daniel Iversen at the near post.
The centre-half almost made instant amends at the other end of the pitch, his header from Paul Gallagher's corner blocked on the line by the keeper with Sinclair following-up to knock the rebound over the line.
But the flag went up for offside against Sinclair and the effort was chalked off.
Browne's red card came in the 38th minute, on the half-way line close to the side of the pitch where the dug outs are.
The skipper and Morsy tangled off the ball, replays showing that the Boro midfielder twice put his arm into Browne's face.
Browne reacted and kicked out, it possibly being the fourth official who saw it and alerted Mr Langford who pulled out the red card.
It is fair to say Browne didn't go quietly, making his protests known and not leaving the pitch straight away.
Three minutes into first-half stoppage-time, Storey got on the end of Paul Gallagher's corner but planted a header down into the ground and it bounced over the bar.
As the whistle blew for the interval, Neil marched on to the pitch and confronted Mr Langford and his assistants.
A word too many out of turn was probably a fair assessment of a one-sided conversation, the referee pulling out his red card for the second time to dismiss Neil.
Jayson Molumby replaced Sinclair at the start of the second half, one which Neil watched from the bottom tier of the main stand - a few rows behind the PNE dug out.
In the 51st minute, Iversen denied Paddy McNair from point-black point, somehow saving his close-range effort with an out-stretched right boot.
The keeper wasn't so fortunate in Boro's next attack, McNair travelling down the right, skipping over Liam Lindsay's challenge and pulling back a cross for Chuba Akpom who blasted a shot against the underside of the bar.
It bounced out to half-time substitute Tavernier who finished the rebound confidently.
That was cue for a double substitution from North End, Emil Riis and Daniel Johnson replacing Tom Barkhuizen and Gallagher.
Iversen saved well again with his feet in the 63rd minute, keeping out Neeskems Kebano's low angle drive from the right of goal.
It became a damage limitation exercise for the 10 men, the hosts not surprisingly seeing a lot of the ball and North End unable to make many inroads going forward when in possession.
There could be an interesting few days ahead as far as the manager's future is concerned.
Middlesbrough: Bettinelli, Fisher, Fry, Hall, Bola, McNair (Saville 57), Howson, Morsy (Tavernier 46), Kebano (Mendez-Laing 82), Bolaise (Johnson 63), Akpom (Fletcher 63). Subs (not used): Spence, Coulson, Watmore, Archer.
PNE: Iversen, van den Berg, Storey, Lindsay (Rafferty 78), Hughes, Browne, Gallagher (Johnson 55), Barkhuizen (Riis 55), Potts, Sinclair (Molumby 46), Evans (Whiteman 69). Subs (not used): Huntington, Maguire, Gordon, Ripley.
Referee: Oliver Langford (West Midlands)