He amassed an impressive three man-of-the-match performances during that time.
Against defending league champions Munster and in front of a crowd of 48,000, Sexton steered over seven penalties to ensure Leinster won a captivating tie back in November.
There were other memorable kicking feats during this time with perhaps the highlight being the injury-time penalty against Montpellier, salvaging a draw away from home.
Sexton would score all of Leinster's points in his man-of-the-match performance at the Rec against Bath in December.
In the return fixture against the English side at the Aviva Stadium, the Dubliner ran the line with efficiency and purpose, scoring a try, six conversions and one drop goal.
Commenting on the award, he said: "We had a lot of tough games over the period and what's been great about it is obviously the results, but also the amount of players we've used over that amount of games.
"Anyone that has got a chance to play has done really well and it has given Joe (Schmidt) plenty of options going forward.
"The first two (Heineken Cup) games put us in a decent position, saving the draw away to Montpellier was, I suppose, crucial. It meant that winning at home against Glasgow put us in a good position.
"But we fixed that at training during the week and we were much more clinical in the home game. It's a different story if you take a couple of early chances, it forces the other team to chase the game a little bit and it creates even more opportunities for ourselves."
Sexton added: "Ian (Madigan) has come in and improved no end from last year. I suppose with the signing of Mat Berquist in the summer it would have been very easy for him to go into his shell.
"But he reacted totally the opposite to that and really upped his performance, his work-rate in training, everything. He's been a great role model to the other younger lads with his attitude and work-rate.
"So we've got a lot of young lads coming through and it's important that they just keep trying to improve. I think that's key for them and you know if they can do that, Leinster Rugby will benefit in the long term.
"We all have really fond memories of the RDS and it's definitely our home. Even though we've played a lot of big games at the Aviva, we definitely regard the RDS as our home and we want to keep our record there really strong and hopefully against Montpellier next weekend we can do that.
"I would like to thank Bank of Ireland for their sponsorship of this award, but most of all to the Leinster supporters who voted for me, I am hugely honoured by their backing."
Winning the monthly award puts Sexton in contention for the Bank of Ireland Player of the Year award which is announced at the Annual Leinster Awards Ball.
Leinster supporters can now vote for the January Bank of Ireland Leinster Rugby Player of the Month.
To vote simply email email@example.com and say which player you think should receive next month's award. Everyone who nominates a player is in with a chance to win a €100 gift voucher.