Poulter, who recently admitted to "throwing away" his chance of winning the Honda Classic, currently sits one stroke behind leader Morgan Hoffman heading into the second round.
Poulter kept up with Hoffman throughout the day as he hit three birdies and an eagle during his bogey-free round.
"Five-under is a nice day," Poulter told Sky Sports 4. "I played lovely today, as nice as I have in a few weeks.
"If I look at the stats of hitting at the proximity to the hole, today would be one of those rounds where I've hit it very close and had plenty of chances. I had a few lip-outs, but no mistakes and a clean card which is key.
"I like this golf course; it sets up good for me. I'm in good form and I'm pretty happy."