He shared a photo on Instagram Tuesday to make the announcement.
The 64-year-old has been undergoing chemotherapy and radiation treatments for several months after he announced in January he had been diagnosed with metastatic prostate cancer.
Sandberg said he plans to continue preventative treatments.
Sandberg, 64, was a 10-time All-Star during his 15 seasons for the Cubs from 1982 to 1997, amassing 282 home runs and 344 stolen bases. After his playing career, he served as manager of the Philadelphia Phillies from 2013 to 2015, going 119-159.
The Cubs are scheduled to unveil a statue of Sandberg outside of Wrigley Field on June 23 -- the 40th anniversary of his best game with the team, when he hit game-tying home runs in the bottom of the ninth and 10th innings and had seven RBIs in Chicago's 11-inning, 12-11 victory over the St. Louis Cardinals.
Sandberg won the National League MVP in 1984, the year the Cubs won a division title. He led the league in triples and runs scored that season while hitting .314 with 19 home runs. He also won nine consecutive Gold Glove awards.
In 1990, Sandberg hit 40 home runs, becoming just the third primary second baseman to reach the 40-homer plateau.
He was elected to the National Baseball Hall of Fame in 2005.
ESPN contributed to this report.