It's 1969 and Penny Chenery (DIANE LANE) is a housewife in Denver raising four kids -- Kate (AJ MICHALKA), Sarah (CARISSA CAPOBIANCO), Chris (SEAN CUNNINGHAM) and John (JACOB RHODES) -- with her attorney husband, Jack (DYLAN WALSH). When she gets a call that her mother has died, she returns to her childhood home in Doswell, VA where her parents ran a successful but now financially struggling horse breeding farm. With her father, Chris (SCOTT GLENN), suffering from dementia, it's up to Penny and her Harvard economics professor brother, Hollis (DYLAN BAKER), to figure out what to do.
Hollis wants to sell the place, but Penny wants to see if she can keep it operational. Taking advice from family friend Bull Hancock (FRED DALTON THOMPSON), she tries to hire semi-retired Lucien Laurin (JOHN MALKOVICH) to be her new trainer, but he's reluctant, telling her that top trainers only work with top horses. Learning she might have one in a yet-to-be born foal that comes from good breeding stock, he agrees. While she loses a "pick the new foal" coin toss with investor Ogden Phillips (JAMES CROMWELL), she ends up getting the horse she wanted and names him Big Red.
The horse is renamed Secretariat by her father's secretary, Elizabeth Ham (MARGO MARTINDALE), who's stayed on to help Penny just like groomer Eddie Sweat (NELSAN ELLIS). After a bad first race, Lucien and Penny convince jockey Ronnie Turcotte (OTTO THORWARTH) to be their new rider, and things take a turn for the better with successive and impressive race wins.
But when Penny's father dies and the family faces a huge estate tax, both Hollis and Jack try to convince her to sell. With the help of Bull's son, Seth (DREW ROY), however, she comes up with another plan. It's then off to the Triple Crown where Secretariat must compete with the speedy horse owned by Pancho Martin (NESTOR SERRANO) and any loss will likely result in Penny losing both the farm and the horse she loves.