The New South Wales state government will also install anti-climb mesh, higher fencing and more cameras to deter people from scaling the world-renowned landmark.
The move comes after a mentally-ill man sparked a major police operation and caused hours of traffic chaos when he climbed the bridge in April during an hours-long stand off in the morning rush-hour.
It took almost six hours to get him down and multiple lanes on the bridge were closed.
"The people of Sydney have had enough of being held to ransom by one person, irrespective of their circumstance, with a personal agenda to seek attention and cause gridlock across our city," said the state's Roads Minister Melinda Pavey.
"While we are sympathetic to someone's personal situation, illegally climbing the bridge is not only extremely dangerous, it also endangers the lives of thousands of drivers who use it every day."
The fine, which used to be Aus$3,300, is now in line with the penalty for illegally climbing the nearby Sydney Opera House. Scaling the Harbor Bridge legally is a hugely popular tourist experience, with more than four million visitors from 140 countries making the ascent under supervision since the climb began in 1998.