The Bora-Hansgrohe rider, who won on his Corsa Rosa debut, completed the 205km Bartali Stage, which kicked off in Bologna, in a time of 4:44:43.
Elia Viviani (Deceuninck-Quick Step) held on for second place, with Caleb Ewan (Lotto-Soudal) third.
“It was my first chance to win a stage and we did it great. I think that all the team is more motivated and it’s good for the next three weeks.”
Team Jumbo-Visma’s Primoz Roglic finished safely in the group and kept his pink jersey as riders head into the 220km third stage, which travels from Vinci to Orbetello.
“We’ll see for how long I can retain the Maglia Rosa. I’ll be the happiest if I carry it in Verona,” said Roglic.
“We enjoy being in this position with the whole team for the moment.”
View more results below.
Stage two results
1. Pascal Ackermann (Ger) Bora-Hansgrohe 4:44:43
2. Elia Viviani (Ita) Deceuninck-Quick Step
3. Caleb Ewan (Aus) Lotto-Soudal
4. Fernando Gaviria (Col) UAE Team Emirates
5. Arnaud Démare (Fra) Groupama-FDJ
6. Davide Cimolai (Ita) Israel Cycling Academy
7. Viacheslav Kuznetsov (Rus) Team Katusha-Alpecin
8. Jasper De Buyst (Bel) Lotto-Soudal
9. Kristian Sbaragli (Ita) Israel Cycling Academy
10. Rudiger Selig (Ger) Bora-Hansgrohe
11. Ryan Gibbons (RSA) Dimension Data
1. Primoz Roglic (Slo) Team Jumbo-Visma 4:47:42
2. Simon Yates (GBr) Mitchelton-Scott +0:00:19
3. Vincenzo Nibali (Ita) Bahrain-Merida +0:00:23
4. Miguel Angel Lopez (Col) Astana Pro Team +0:00:28
5. Tom Dumoulin (Ned) Team Sunweb
6. Rafal Majka (Pol) Bora-Hansgrohe +0:00:33
7. Tao Geoghegan Hart (GBr) Team Ineos +0:00:35
8. Bauke Mollema (Ned) Trek-Segafredo +0:00:39
9. Damiano Caruso (Ita) Bahrain-Merida +0:00:40
10. Pello Bilbao (Spa) Astana Pro Team +0:00:42
73. Ryan Gibbons (RSA) Dimension Data +0:01:46