Robert De Niro’s personal trainer of 40 years described him as a generous boss who treated him well — while detailing the close relationship they built through daily, rigorous work-out routines during testimony in the actor’s ongoing legal battle with his ex-assistant.

Dan Harvey, 63, told a Manhattan federal court jury Wednesday that De Niro, 80, never cursed him out or used profanity in the decades they’d been working together, but conceded that the “Mean Streets” actor sometimes yelled at him when the two men were younger.

“When I was younger it happened a lot. Not so much anymore. I sort of know the ropes, so to speak,” Harvey testified.

Their workout sessions — which vary based on what role De Niro is prepping for — typically last between two to seven hours on an almost daily cycle, and Harvey estimated that in the last 365 days, he’d spent 310 of them with the Oscar-winner.

Harvey’s account countered the accusations from Graham Chase Robinson, 41, who described De Niro as a hellish boss who frequently berated her with expletive-laden tirades in her $6 million lawsuit against the actor, which she filed in 2019 after he sued her for $12 million for allegedly stealing millions of frequent flier miles from him.

She also accused De Niro of relegating her to stereotypically female tasks like doing housework and running errands, despite holding the self-created title of Vice President of Production and Finance.

When Robinson’s attorney asked whether De Niro ever made Harvey run errands like picking up coffee, he said at some point he probably had.

“I mean, I’ve been working for him for 40 years. I’m sure I got coffee for him at some point,” he testified. “It’s not my job. There’s assistants and PAs and drivers who do that stuff.”

Harvey first started working with De Niro in 1984 after the Manhattan-born actor had finished shooting the boxing movie “Raging Bull.”

“He was looking for a trainer to help him lose the 35 pounds that he had from the movie,” Harvey testified, explaining that before long he was helping De Niro practice his lines during workouts.

“We would be working on dialogue and he would work with me, two hours training, then maybe walk the treadmill slow, working his dialogue, running his dialogue with me,” he said.

“He literally walks in and starts talking to me. He starts the first scene of the day and he’s queuing me… As soon as he walks into the door… He wants to roll and run the next scene the next day.”

Over the years, Harvey said he travelled the world with De Niro, training him for months at a time on movie sets in countries including Argentina, Brazil, Russia, New Zealand, Australia, Mexico, England, France, Italy and Hungary.

Training methods changed to meet the needs of the role De Niro was playing, Harvey said, recalling how the ending of 1990’s “Goodfellas” required the actor to look older than he did throughout the rest of the movie.

“We went and trained 21 days straight in Montauk to make him look a little bit older and gaunt,” Harvey said.

Other movies, like “Cape Fear” the following year, required De Niro to look “very lean, defined and cut up.”

Harvey said De Niro paid him a $290,000 salary before 2019, which was bumped to $375,000 in May of that year.

During the 2008 financial crisis, he tried to cut it by 50% but Harvey asked him not to.

“I explained to Mr. De Niro that getting a 50% pay cut at this point was just not going to work with me. I told him I have a mortgage payment, I have car payments and it just didn’t make sense for me,” Harvey testified.

“He said he would totally understand and take care of it.”

Robinson — who started working for De Niro in 2008 — asked for a pay raise 10 years later to match what Harvey was making.

She previously testified that De Niro initially brushed her requests off.

“Chase you don’t have kids. Dan has a family to support,” she said he told her.

De Niro ultimately agreed to pay Robinson a $300,000 salary.

During closing arguments later Wednesday, De Niro’s attorney Richard Schoenstein said Robinson’s claims of gender discrimination were non-existent until she learned the actor’s company, Canal Productions, was looking into her finances from her time there.

“The idea of gender discrimination did not come up until lawyers got involved,” he said, later adding, “Gender discrimination is still alive and well in this country, but we have to be able to distinguish real gender discrimination and what happened here.”

De Niro filed suit against Robinson against her shortly after she left Canal in 2019, claiming she stole about $60,000 worth of frequent flyer miles, some of which he had allowed her to use under an “honor code.”

Schoenstein argued Robinson clearly snatched miles from the actor as soon as her job appeared to be in jeopardy.

“She never moved a million miles at once. And then all of a sudden in early 2019, with all of this stuff going on… all of a sudden she sweeps 5 million miles into her account,” he told the jury.

Robinson’s attorney, Brent Hannafan, argued during his closing arguments that his client had bravely stood up to De Niro — who he described as “one of the most well-known, powerful men in the entertainment industry” — even as she feared retaliation from the star and his staff after she quit.

“We ask all of you to stand up for your beliefs and exercise your power as a jury,” he said.

Schoenstein argued those fears of retaliation were also made up.

“Only after being called out on her spending did she say anything about retaliation,” he said.

De Niro, who was in court for part of the closing arguments, did not comment as he left.

Jurors are set to begin deliberations Thursday.