The Swede, driving a Skoda Fabia Rally2, made a slow start and found himself at the bottom of the leaderboard after Friday’s opener.
Undeterred, his confidence and pace grew with each kilometre and, when Adrien Fourmaux picked up a rear right puncture during the second pass of Cinturato, Tidemand was well-placed to inherit the lead.
"It's very slippery, but the feeling is okay. We will see what happens next and I think tomorrow will be completely different," said Tidemand, whose overnight advantage is just 6.8sec.
Fourmaux’s position really didn’t do him justice. He and his M-Sport Ford Fiesta Rally2 were in formidable form during Friday’s morning loop and the Frenchman claimed three impressive stage wins.
Mads Østberg was 5.6sec further back in third and reluctant to take any risks so early in the event. The Citroën C3 R5 pilot is fighting head-to-head with Tidemand for the series crown and could mount an attack over Saturday’s mountain stages.
Jan Kopecky rounded out the leaderboard in fourth, 19.9sec adrift of Skoda team-mate Tidemand up front. A Tarmac specialist, Kopecky was surprised at the loose conditions and found it difficult to enjoy the stages.
Full coverage from ACI Rally Monza is available on WRC+ All Live here, including every stage broadcast as it happens as well as key interviews, features and expert analysis from the service park.