Director of engineering Ayao Komatsu says that the Englishman, who had a run in a two-year Ferrari SF21 as part of his preparation for his race weekend debut, "didn't put a foot wrong."
He ended the session in 15th place, three spots and 0.3 seconds behind team-mate Nico Hulkenberg, who is celebrating his 200th grand prix in Mexico.
"I don't think we can fault him," said Komatsu. "He's done really well, all the way from the very initial preparation he's been very professional, very, very easy to deal with.
"And then every single process I've nothing to complain. And today with a calmness he understood the objectives of every single run.
"He didn't put a foot wrong, really. He didn't maximise the soft lap, the time difference, Nico's lap wasn't great either, so you can't really read too much into it.
"But in terms of his feedback, it was really good engagement with his engineers. Very, very good job. Very impressed.
"Honestly, I can't pick a moment where from all the way through the preparation, something was frustrating or difficult, including his management, it's been a really smooth process, it's been a real pleasure to work with him and his management team."
Asked if the 18-year-old had actually exceeded expectations, Komatsu indicated that he had.
"I don't think you can expect much better," he said. "And then certainly, better than my expectations as well.
"Not that my expectation was low, but that was so professional. And he didn't put a foot wrong. And the communication and the feedback was really good as well. So really, I've got nothing to complain about. So it was a really impressive FP1."
Haas has run many rookies in the past, including Charles Leclerc.
Asked how Bearman compared, Komatsu said: "I think it's a bit difficult to make a direct comparison, really. But honestly, if I just think about today, he's done so well. Really, really, well. I really can't fault him today.
"So we've got another session planned with him in Abu Dhabi. So really looking forward to that. And then yeah, hopefully more sessions next year as well. So it's very promising."
