Earlier this year, Monchengladbach revealed that Lainer would be missing "for several months", having been diagnosed with lymphoma.
However, a further statement from the German club on Monday revealed that the 31-year-old had "successfully completed the therapy that he has been undertaking", and the Austrian was able to train alongside his teammates on Tuesday.
"Stefan Lainer is set to return to training for Borussia Monchengladbach. The right-back, who was diagnosed with lymphoma in July, has successfully completed the therapy that he had been undertaking over the past few months," read the statement from the Bundesliga club.
"A recent final examination showed that therapy had been successful for Lainer and that he had been cured of lymphoma."
Lainer has played 125 times for his current club, scoring four goals and registering 13 assists, including 18 appearances during the 2022-23 campaign.
"I'm thrilled that I can once again fully concentrate on football and train together with the team," Lainer said in a statement. "The last weeks and months were a big challenge. I'm very thankful to have had so much support from my family, my friends, the club and the fans during this period.
All this gave me strength. In particular, I would like to thank my wife and Dr. Sellmann, who were the most important sources of support during this time."
Meanwhile, Monchengladbach's managing director for sport Roland Virkus added: "We're incredibly happy and also relieved that Stevie Lainer has won the battle against this illness. This triumph makes us very happy. We're pleased for Stevie and his family.
"The fact that he's now back with the squad and can see the other lads on a regular basis is an important step forwards. At the same time, we'll give him the time he needs to make a full comeback."
Monchengladbach also revealed that Lainer has been able to "regularly work on his physical fitness" during his treatment, suggesting that he will be able to return to action in the not too distant future.
"The 31-year-old was able to regularly work on his physical fitness with fitness coaches at BORUSSIA-PARK during the months of therapy - he was under close medical supervision," said the club.
"This allowed Lainer to stay in good physical shape. Following the completion of obligatory performance diagnostics, Borussia's right-back will be integrated into team training step-by-step, starting this week."
Monchengladbach will be aiming to extend their unbeaten run in all competitions to five matches when they take on Borussia Dortmund in the Bundesliga on Saturday afternoon.