The leave is part of their unrecorded leave, which is capped at 14 days a year and typically used for approved reasons such as parental care and marriage.
Civil servant Mok Yee Soon, 28, who volunteers with Lion Befrienders, said: "It gives me more opportunities to volunteer based on the charity's needs."
Social and Family Development Minister Tan Chuan-Jin lauded the move, saying on Facebook that the government should walk the talk.