Brown helped himself to his first-ever two-goal return in league football as the Blues picked up a massive 3-1 win at AFC Wimbledon.
It means their play-off hopes are in their own hands with a single game of the regular season to come against Accrington Stanley next Sunday.
Brown’s two goals in first-half stoppage time turned the face of the game on Pompey’ first visit to the new Plough Lane.
The left-back played down the quality of his finishes on a day for his team to savour on his return after injury.
He said: ‘I couldn’t believe I found myself up there, to be honest!
‘Me and Ronan do usually get forward quite well really, so it was pleasing.
‘I found myself with quite a bit of time for the first and second one.
‘It was just about concentrating and striking the ball well.
‘I don’t know what I was doing for the second one, to be honest!
‘It went off my foot and into the back of the net.
‘It got stuck under my foot, to be honest, so I just tried to make any connection I could - but I’m not complaining!’