The Magpies forward found the net four times in three Premier League appearances during the month, including a brace of penalties in the memorable 4-3 comeback victory over West Ham.
After scoring his 15th league goal of the season, the Sweden international credited his recent run of form to the supporters and his teammates.
"It's always nice to feel appreciation from the fans who voted for this award," said the 24-year-old.
"I think the consistency of playing time has allowed me to get to my best level recently. As well as scoring goals, I feel that I'm performing well overall, so it has been a rewarding period. With the team and the players we've got, it's easier to find your best form."
While reflecting on the past month, Isak cited last weekend's win over the Hammers as one of his highlights of the season so far.
"That was amazing - it's the type of game you want to be involved in as a player," he said. "It's a great memory for the team and the fans, and one we'll remember for a long time.
"We're now focused on grabbing points by winning as many games as possible for the fans between now and the end of the season. We want to enter into Europe, and we have that chance, but we'll take it one game at a time and try to climb as high as we can in the table."
Voting for the Sela Player of the Month takes place after every match in the club's post-match email.
To ensure you receive the post-match email - which includes highlights, interviews, stats from the game and more - make sure you have 'news' ticked within preferences in your Newcastle United account. If you don't have an account, you can sign up here.