Alex Kenyon trebled his tally for the club in one afternoon with two goals, while Padraig Amond secured all three points in the closing stages with a stunning strike.
The win extends the Shrimps’ unbeaten run to five games, though the seven-point gap to the play-offs will likely prove too much to overcome with four games left.
However, Bentley was delighted as his side made history with the 3-1 victory against Pompey.
He said: “It’s a great day for the club to to get a win over a very big club.
“Our home record hasn’t been good and we wanted to give our fans something to cheer about and I’m sure they will have gone home happy after that.”
Kenyon opened the scoring with a 10th-minute header and made it two with a stunning volley in the second half.
Pompey pulled a goal back six minutes from time through Conor Chaplin’s first senior goal but Amond struck in stoppage time with a stunning left-footed volley from the edge of the area.
Bentley was thrilled with his side’s performance and the quality of the goals they produced.
“Everyone played their part and we scored some really good goals as well with Alex Kenyon and Padraig Amond hitting two top quality strikes, ” said the manager.
“We played some great stuff at times and the only thing I was disappointed with was that we didn’t keep a clean sheet.
“Their goal gave them a bit of a lift and it would have been a travesty if we hadn’t hung on for the win but thankfully we hit them with a wonderful third to take the points.”
The day was also soured for Pompey by a worrying injury to Josh Passley who was knocked unconscious and had to be taken to hospital following an eight-minute delay.
Awford confirmed the defender was conscious when he left the ground but admitted: “He’s not in a great way.”
Portsmouth have now lost three of their last five games and Awford was left bemoaning his side’s defending.
He said: “There wasn’t a lot in the game to be honest but we have been hit by two set-pieces which is really disappointing.
“We have done well in that area this season and we do work hard on that part of our game but today we were not sharp enough and they made us pay and overall that proved to be the difference.
“We played some decent stuff and if Jed Wallace hadn’t seen an effort cleared off the line at the start of the second half it could have been a different game.”