Bruce Stewart gave his family his usual "loving farewell" when he left on Monday morning for work, but he never made it there.

The 44-year-old father-of-two left his home on Potts Street in Ryde about 7.30am, heading in his 2002 blue Holden Astra sedan towards the high school in Sydney's western suburbs where he works as a teacher librarian.

Bruce Stewart, 44, didn't show up for work on Monday and his family hold grave concerns for his safety.

His wife, Melissa Stewart, said he "made brief contact with some close friends before not responding to any calls or messages, which is very, very unlike him."

Police have since issued a missing person alert for anyone who may have seen him.