Both burglaries occurred on Wednesday night, with the first reported at 6:40 p.m. in the 700 block of Anacapa Lane and the second reported at about 9:10 p.m. in the 500 block of Nottingham Lane, according to police.
In the Anacapa Lane incident, a young resident saw the suspect, who entered the home through an unlocked ground floor window. The suspect did not confront the victim, and fled without taking any property, police said.
The suspect is described as a white man in his 20s who is about 5 feet 10 inches tall with brown hair, and was wearing a black shirt and light blue jeans, according to police.
Later that night, the second burglary was reported less than a half-mile away on Nottingham Lane. The suspect shattered a window to enter the home, and took a piece of jewelry, police said.
The homeowner encountered the suspect, who ran away from the home. The suspect is described as a man who is about 5 feet 9 inches tall with an athletic build, and was wearing a black hooded sweatshirt and dark pants, according to police.
No arrests have been made in the two cases, which are not believed to be related.
Anyone with information about the burglaries is encouraged to call Foster City police at (650) 286-3300 or the department's tip line at (650) 286-3323.