The 25-year-old enjoyed two years with Nürnberg but was released this summer and despite having plenty of options, the German opted to stay in his home country and play in the Bundesliga.
Blum's deal with Frankfurt will run out in 2017 but there remains an option to extend it a further two years.
The New Addition
The club's sporting director Bruno Hübner spoke about the new signing, saying: "With Danny Blum, we get a very fast player with a good shooting technique and can be used in several positions."
Meanwhile, Blum himself talked about joining Eintracht Frankfurt and highlighted that while he had "several options home and abroad," he was intrigued by Frankfurt's offer.
"As the interest of Eintracht Frankfurt came, I knew immediately I would like to take this option...I look forward to the extraordinary atmosphere at Commerzbank-Arena and the fantastic audience."
Blum recently played against his new club as FC Nürnberg and Eintracht Frankfurt squared off in the relegation play-off for a spot in the Bundesliga.
The 25-year-old featured in both legs as his side fell 2-1 on aggregate to Frankfurt but the midfielder now gets his chance to play in the Bundesliga with the side that dashed those hopes just months ago.
Frankfurt May Not be Done
Frankfurt continue to strengthen their side as they hope to avoid another relegation threatened season and could finalise a deal to sign Ante Rebic in the coming days.
The 22-year-old is currently at Fiorentina but could make the switch to the Bundesliga side soon after two loan spells with RB Leipzig and Hellas Verona. Rebic's arrival would add another attacking option for an Eintracht Frankfurt side in desperate need of strength going forward.
(Quotes via eintracht.de)