It is reported queues stretching back to the M90 at Masterton and Pitreavie, while STV said police have also been called after several drivers were reported for using the bus lane on the bridge.
Traffic was switched from the Forth Road Bridge in the early hours after a series of bridge walks and the official opening by the Queen.
The new bridge was only open for two days last week and extra traffic is expected as more motorists take the opportunity to cross it for the first time.
No official traffic figures have been published, but it is thought that as many as 100,000 vehicles may have crossed on the first day last Wednesday, compared to the 80.000 average on the Forth Road Bridge.
Tailbacks of at least five miles built up in each direction.
Inspector Peter Houston of Police Scotland said: “We do expect there to be long delays as people come to see the new bridge over the coming days.
“We would advise members of the public who currently cross the Firth of Forth as part of their commute to think about disruptions to their journey and to allow for extra travel time as traffic levels adjust.
“Those who are travelling to the crossing for non-essential journeys are asked to consider very careful the timings of their visit and whether their journey is necessary.
Stein Connelly, operator manager of the official Traffic Scotland information service, said: “Demand for using the Queensferry Crossing when it first opened last week was very high.
“People were understandably coming to see the new bridge and this did lead to congestion.
“With the Crossing reopening tomorrow we would urge road users to plan their journeys.
“Traffic is likely to be very heavy and long delays are possible.”
All traffic apart from pedestrians and cyclists will use the new bridge until late October when new links with the Forth Road Bridge are due to be finished so it can be used by buses and taxis.