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.
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.
"We are asking the public to please keep looking for him, and contact police immediately if they can help," Ms Stewart said on Tuesday morning.
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"We are distraught. He is our world, a devoted father and husband, adored by all who know him, and we are desperate to find him."
Mr Stewart is described as being Caucasian in appearance, about 185cm tall with short light-coloured hair and cropped beard with flecks of grey.
The vehicle he was driving has faded blue paint with NSW registration CA29HZ.
If anyone knows the whereabouts of Mr Stewart, they are urged to contact police at Ryde Police Area Command, or Crime Stoppers on 1800 333 000.