The deal has just been confirmed after backman Dylan Roberton announced on Friday that he would step away from footy in 2019.
“It was important for Dylan to have the time to make a decision that was right for he and his family,” St Kilda’s General Manager of Football Simon Lethlean told the club’s website.
“Once we were aware that he would be missing the season and moving onto the long-term injury list, we decided to bring Sam in.
“The reality of football is that we need to utilise the AFL rules to best prepare our list for the rigours and requirements of the competition, and Sam provides an important element heading into the season.
“He’s an experienced defender, who can also play forward if need be and pinch-hit in the ruck.
“He is also a quality person who knows what is required at the elite level.”
Rowe, who was delisted at the end of last season by the Blues, was set to play with Doncaster East in the Eastern Football League in 2019.
The 199cm defender played 99 games with the Blues over a six-year period from 2013 to 2018.
The pair will compete for a spot in a stretched St Kilda backline.
The Saints begin their 2019 season with a crucial home game against fellow preseason strugglers Gold Coast on Sunday 24th March.