Drivers have faced delays during 730 overnight closures and 12 weekend contraflows during work on the A58M, which is used by more than 80,000 vehicles a day.
A total of 2,630 cubic meters of concrete and 550 tonnes of steel reinforcement were used during work on the tunnel, which supports structures including Leeds General Infirmary,.
Lighting has also been updated with LED technology in the tunnel, which was first opened in June 1966.
Coun Richard Lewis, Leeds City Council’s executive member for regeneration, transport and planning, said: “We are delighted that these improvement works to Woodhouse Tunnel have now been successfully completed.
“It was a very difficult technical challenge working on a tunnel which is more than 40 years old on a key road for the city which is used by 80,000 vehicles every day, but with our officers working alongside Carillion it has been a success.
“A lot of people have already commented on the new lighting in the tunnel, and for that I’d like to thank our partners TVL and SSEC for their efforts. I’d also especially like to thank the NHS Trust, University of Leeds and everyone in the city for their patience while this essential work was being carried out.”