The campaign has been launched by the magazine 11Freunde (11 Friends) and includes statements from several Bundesliga stars, including Hertha Berlin's Dedryck Boyata, Borussia Mönchengladbach's Christoph Kramer and FC Köln's Jonas Hector.
The latest issue of the magazine features a number of different cover stars holding signs that read: "You can count on us!" Fans have also been sharing images with the same message on social media.
"Even in 2021, there will not be a single openly homosexual footballer in the German men's professional leagues," said a statement from the players backing the campaign.
"The fear of being attacked and ostracized after coming out and of jeopardizing one's career as a professional footballer is apparently still so great that gay footballers believe they have to hide their sexuality.
"No one should be forced to come out. That is the free decision of each individual. But we want everyone who decides to do so to be sure of our full support and solidarity.
"Because it is one of the elementary freedom rights of every human being to be able to confess his or her sexual orientation ... that is why we say to all those who are struggling with this decision: We will support and encourage you and, if necessary, also defend you against hostility. Because you are doing the right thing, and we are on your side."
A number of clubs also voiced their support for the campaign on social media, including top tier sides Köln and Freiburg.
Meanwhile, Thomas Hitzlsperger, the former German international who came out as gay following his retirement from professional football in 2014, tweeted: "Another step in the right direction -- well played, 11Freunde."
Football still has much work to do when it comes to improving attitudes toward the LGBTQ community.
In the English game, for example, a report by anti-discrimination group Kick It Out revealed a 95% rise in reports of abuse based on sexual orientation during the 2019/20 season.
Kick It Out also ran a YouGov poll of 1,000 fans, 32% of whom said they had witnessed homophobic chants at games between January and December 2019.