His big brother, John, never played at football's highest level and instead might motivate his Baltimore Ravens with examples of sacrifices by military members in real-life conflicts.
The Harbaughs, separated in age by all of 15 months, took different paths to the doorstep of the Super Bowl. Now, they're sparking talk of a "Superbaugh."
Baltimore plays at New England in Sunday's first game for the AFC title, then San Francisco hosts the New York Giants for the NFC crown. Their parents, Jack and Jackie, plan to watch on television from home in Wisconsin.
While the brothers have spoken during the playoffs, Jim is quick to point out they are each handling business their own way.
"Each situation is different," he said. "There are some similarities, there are some differences. Their situation is similar in some ways, and different in others. We're each going to handle it accordingly."
Jim Harbaugh was a star college quarterback at Michigan, a first-round draft pick and eventual Pro Bowler who turned to coaching much later. His thick offensive playbook featuring a version of the West Coast offense can be overwhelming, and Harbaugh has been known to mix in some twists, such as using David Akers to throw a pass on a fake field goal or throwing to a nose tackle-turned part-time fullback.
He gets a kick out of the game-planning process and throwing in some new wrinkles each week.
"Really enjoyable. Yeah, it's a fun part of the job, and I think the thing that makes it fun is that the players are really stimulated by that," Jim Harbaugh said. "And we've got smart guys that they want it, they almost need it. And really keeps them on a razor's edge."
Throughout the season, the Harbaughs talk regularly to share ideas, yet suddenly are in scouting mode with the potential for another history-making matchup next month in Indianapolis. On Thanksgiving night, they became the first brothers to face each other as NFL head coaches.
"Had a chance to watch his game, and found myself, as always, pulling very hard for him and his team. Very happy for his success," Jim said. "(I watch) as a brother, as a fan of his team, and also as a possible opponent, yes."
One thing neither likes during game week is anything they consider nonsense - a distraction to the one and only goal of a victory.
The Harbaughs can be dismissive. They're known to sneer or blow off questions altogether when it comes to injuries or any other tidbit that might give an opponent insight or a possible advantage - perceived or otherwise.
His message: "Don't overcook it." Translation: Stick with what got you here.
Both possess a laser-like football focus and find unique ways to motivate.
"When he gets fired up, it's fire and brimstone," Ravens linebacker Jarret Johnson said of John. "But for the most part, he reads a lot. He draws a lot from the military. We get a lot of poetry. He uses a lot of different analogies and stuff. I would say he's all over the place. He's a rah-rah guy when he needs to be, and he's also very subtle. Maybe a Shakespeare speech, something like that. He draws inspiration from everywhere."
Jim has his players buying into a blue-collar mentality, and there are actual blue-collar shirts to fit the theme. Defensive line coach Jim Tomsula wears his regularly around team headquarters.
"It's really been fun to see the sayings that have really grabbed on from the blue-collar aspect," Akers said. "A lot of this country is built on the blue-collar idea."
"He just tells us to give it all we have, give it all we've got, go out there and just fight, just fight as a team," running back Frank Gore said. "Think about all the bad times we had here and now we have this opportunity and go take advantage of it. That's what we're trying to do."
If Jim Harbaugh wins Sunday, he'll be headed back to a city where he is still loved despite not coming through that day. His sister, Joani Crean - whose husband coaches at Indiana - still regularly gets stopped by strangers when she travels to Indianapolis with their stories about her brother, Jim.
Both Harbaughs recall their youths to give examples of what they learned from their coaching father, Jack.
"The guys laughed. They've heard it before, but when you say, `This is something my dad used to tell me,' boom, it disarms them a little bit. They appreciate it," he said.
John also took part in an NFL-USO coaches tour of the Persian Gulf in 2009 and occasionally calls on military personnel to address the team after practice. In turn, in 2010 he spoke to the Army's 1st Cavalry and attended its team-building symposium.
"Those guys have so much at stake. It's hard for us to even look at it and say it's the same, but when they teach their troops, they make sports analogies all the time," Harbaugh said. "I think that's ironic, because we make military analogies all the time."
His brother has his own methods - and the 49ers have been all in since the start. San Francisco has gone from a 6-10 team last season, one that missed the playoffs for the eighth straight season, to a 14-3 team one win from playing for football's biggest prize.
He is rah-rah to the core. At the same time, he has been known to sleep at team headquarters while "honkering down" as he calls it. Harbaugh orders pizza to team headquarters as he and his staff spend hours in the film room studying opponents.
Players walk around wearing T-shirts with Harbaugh's catchphrase "Who's got it better than us? No-body!" That one came from his father.
"I'll pick up an article or a news story and you see something in there I'll think,
Hah, where have I heard that?"' said Jack Harbaugh, whose credo was born in his tiny hometown of Crestline, Ohio. "I was talking to my cousin, Mike Gottfried .. and he said:You know, it's amazing. I can recall that in Crestline back in the early 1950s.' ... Mike says:
You know what? I can recall that.' We'd be walking out to play. Or we'd be going home at night and we'd look at each other say,Who's got it better than us? Noooo-body!' And that was a great life."
Life will be much sweeter for the close-knit Harbaughs if each brother holds up his end of the bargain Sunday. Then, it will be reunion time in Indy with the world watching.
AP Sports Writer David Ginsburg in Baltimore contributed to this story.