Nordgren, 30, played for the University of Texas and the Philadelphia Eagles before appearing on the reality TV series "Most Eligible Dallas."
"He's a great influence on her, and her friends and family love him," an insider close to the 27-year-old actress told UsMagazine.com.
"He's older, a successful businessman, and he has been a great friend to her," the source said. "He's also a Christian and won't drink around her. He's trying to keep her sober and on the straight and narrow. He's really good for her."
The New York Post said the pair have been friends for about seven years, but only recently started dating.
Lohan recently completed a 90-day, court-ordered rehab stay.
The actress was under court order to undergo in-patient treatment for substance abuse as part of her conviction for reckless driving and lying to police.
The "Mean Girls" and "Freaky Friday" star's once-bright career has been eclipsed by her battles with drug and alcohol addiction, motor vehicle offenses and other legal woes.
The Oprah Winfrey Network was reported to have paid the troubled actress about $2 million to star in an eight-part docu-series about her efforts to remain sober and revive her career. She was most recently seen in the low-budget film "The Canyons."