The company also announced Wednesday that it will add some small gasoline engines to the Spring Hill complex.
The additions will bring more jobs to Spring Hill, but a spokesman wouldn't give specifics on how many would be added to the sprawling former Saturn facility about 40 miles south of Nashville.
All GM said in a statement is that the SRX and a yet-to-be identified second midsize vehicle would "create or retain" about 1,800 jobs, while a $185 million investment in the Spring Hill engine factory would keep 390 jobs.
The complex now employs just over 2,300 workers, including hourly and salaried employees and those who work for parts supply companies.
Last year GM announced plans to invest $350 million in the Tennessee assembly plant to build two future midsize vehicles. The plant already builds several small gasoline engines plus the Chevrolet Equinox midsize SUV.
GM also announced Wednesday that it would invest just under $50 million at its Bedford, Indiana, engine block casting plant, keeping 45 jobs.
The company was holding a news conference at the Spring Hill factory on Wednesday to formally make the announcements.
The Cadillac SRX now is built at a GM factory in Ramos Arizpe, Mexico. That plant also builds the Chevrolet Sonic subcompact car and Chevy Captiva small SUV.