An employee at the Owings Mills library also tested positive last week, and that branch is scheduled to reopen next week.
In a statement, the library system advised users who visited any of the three branches within the past week that they may choose to be tested for the virus.
Curbside services and computer appointments will once again be offered at the Parkville-Carney branch at 9509 Harford Road on Tuesday and at the Cockeysville branch at 9833 Greenside Drive on Friday.
The Owings Mills library branch will be closed for cleaning until Nov. 19, according to the library system.
Book drops remain open at those locations, and the library is offering virtual programming on its website.
Staff members who worked in close contact with the employees who contracted the virus have been instructed by the Baltimore County Department of Health to self-quarantine, according to the library system.
The employees did not encounter staff members at other branches, which remain open for curbside pickup and printing.