The 44-year-old received the diagnosis "following extensive tests with medical professionals", and faces a period of absence and rehabilitation.
Bentley told the club's official website: "At the start of the year I had some chest pains whilst doing a bit of training.
"After getting checked out I was told I had a blockage in one of my arteries. I had some more tests and was placed on medication to help my condition.
"Due to the Covid situation, I haven't been able to get into hospital, but I finally went in to Liverpool Chest & Heart Hospital this week to have a coronary angiogram and stent fitted, but whilst the doctor was carrying out the procedure he noticed that my condition was a bit worse than first thought.
"It was then recommended I have a heart bypass instead. It's not the news I wanted but I am thankful I got checked out when I did as this could have been a lot worse.
"I'm looking forward to getting sorted and being back fit doing the job I love as soon as possible."
Bentley resigned from his job at Sky Bet League Two Morecambe last October following the departure of previous Fylde boss Dave Challinor.
But the club struggled through the campaign and sat second from bottom of the table and facing relegation when the season was curtailed due to the coronavirus pandemic.
Fylde chief executive Jonty Castle, said: "Jim's a popular figure at Mill Farm amongst the staff, players and the fans, so all of us will be looking forward to him returning as soon as he can to lead the club in our 2020-21 campaign.
"Until his return, we will all be continuing the hard work behind the scenes and giving Jim our full support with anything he may need to help with his recovery."