The retired Marine Corps former four-star general has received stock and option awards as a board member of General Dynamics since August 2013. In 2015, those equity awards exceeded $140,000 in value, and the prior year they topped $112,000. There's also cash compensation given to the board members.
To avoid conflicts, analysts say Mattis will likely be required to put any defense-related holdings in a blind trust or sell them outright. Moreover, he would want to guard against the appearance of conflicts and remove himself on any dealings involving the Virginia-based company.
"He would have to resign the board and do something about any holdings to avoid any conflicts of interest," Cowen analyst Roman Schweizer said Friday. "But that's pretty standard for anyone going into U.S. government, and would include any other defense-related holding in his case."
General Dynamics declined to comment. The Trump transition team did not immediately respond to CNBC requests for comment. Mattis could not be immediately located for comment through General Dynamics or through the Hoover Institution, where he has been a visiting fellow.
Experts say it's not unusual for high-level executives at defense companies to serve in senior positions in the Pentagon. They noted that that Mattis served in the military for some 44 years, retiring in 2013, and spent just a few years in the private sector at a defense contractor.
Candidate Trump pledged to add more ships, aircraft and troops to the military. Industry analysts have suggested that adding more active-duty troops in the Army and Marine Corps would be good news for munitions companies such as General Dynamics and Orbital ATK.