The deal was announced days after its bid to take over Bumble Bee Seafoods was foiled. The value was not revealed.
In a statement, TU said the is expected to be completed by the end of January 2016 subject to German authorities' approval.
“Germany is one of the largest seafood markets and part of our strategic pillars for growth in Europe. Through this partnership with Rugen Fisch, Thai Union becomes a market leader in Germany and further strengthens its position as one of the European seafood leaders," said Thiraphong Chansiri, president and CEO of Thai Union.
Rugen Fisch's leading brands include Rügen Fisch, Hawesta, Ostsee Fisch and Lysell.