The Juventus midfielder is expected to sign for Liverpool this week on a three year deal as a replacement for Javier Mascherano. Agger, who is an international team-mate of Poulsen, says his fellow Dane would be a good addition to the Reds' squad.
"Christian is more than welcome in our club. Christian would be a perfect addition to most of the big clubs in Europe, so he will certainly fit in here," said the defender.
"He is a top player and will make us stronger. We need to have big signings so we can compete and he is one of those players.
"Christian will improve the team. But we need more improvements if we want to be at the top of the league this season.
"Maybe he will find the pace of here a bit of a culture shock; he will have to get used to the extra high tempo and he won't be able to drink café lattes like he does in Italy!
“He has played in Italy, Spain and Germany and done very well, so I don't see any reason why he shouldn't be a success with Liverpool.
"Of course it will be nice to speak some Danish in the dressing room but that is not what counts. The most important thing is that we add to the quality at the club. We have Mascherano but it looks like he is leaving so there is a gap there.
"I have spoken to Roy but Roy knows him so well that I couldn't tell him anything that he did not know. Christian is a very good football player."