Haller was diagnosed with the disease a few weeks after joining Dortmund from Ajax Amsterdam in July for €36m and is yet to make his debut for his new side.
Haller had to undergo chemotherapy after the tumor was found to be malignant.
“Happy New Year to all! And it’s off to a great start for me because it means getting back on the field,” the 28-year-old Ivory Coast international wrote on Twitter, posting images of him working out at the gym.
“2022 wasn’t the easiest year but it prepared me for all the new challenges that 2023 will bring.”
In a video message posted by Dortmund Haller said: “I’m finally back. It was not that easy but with your support it was better and easier to do, so I am just looking forward to seeing you in the stadium for some victories.”
Haller was the third top scorer in the Champions League last season with 11 goals, behind only Robert Lewandowski(13) and Karim Benzema(15).
The former Eintracht Frankfurt and West Ham United frontman struck 47 goals and provided 16 assists in 65 appearances across all competitions for Ajax after joining in January 2021, winning two Eredivisie titles and two Dutch Cups.
Dortmund find themselves in sixth position on the league log and return to action on January 22 against Augsburg.
Edin Terzic's side will also face Chelsea in the Champions League round of 16 stage next month.
