Adams won Premier League titles playing alongside Keown in Arsenal's back four.
"Koscielny was brilliant [at the end of last season]," Adams told Arsenal.com.
"He reminds me a lot of Martin Keown. He's very tenacious. I hate labelling people because Martin Keown was one of the best we've ever had. But there are similarities there, the way Koscielny marks and his last-ditch tackles.
"He's tenacious in the tackle. [When it came to] that tight, one-to-one defending, there wasn't a better player that I've played with, [than Keown]. To put Koscielny in the same category [to Keown] is an enormous compliment I think."