Kozluk, 31, joined the Reds in the summer of 2007 from rivals Sheffield United and has made 68 appearances for Barnsley at both left and right back.
He told www.barnsleyfc.co.uk:
"It is the perfect deal for me. As soon as the season finished Simon (Davey) told me he wanted me to stay and there was never any question if me going anywhere else. It was just a case of getting back from holiday, coming into the club and signing the deal.
"There was interest and Neil Warnock offered me a three year contract with Crystal Palace but I did not want to leave Barnsley. Hopefully now all that speculation will be put to bed because I want to be here. I could have jumped ship but my family is settled and I am enjoying my football. I love it here.
"Anything is possible next season and picking up ten more points over the course of the season is nothing really. Just look at what Burnley achieved last season - no one would have believed that was possible so anything can happen. We threw away so many points in the last few moments of matches and it really left the manager scratching his head at times because he was the one who took all the flak when we let games slip away.
"It seems to have been a long summer and we have almost had two months off. We should all be fresh and raring to go in pre-season next week".
Reds boss Simon Davey also spoke about tieing Kozluk down for another year:
"We are delighted that Rob has pledged his future to the Club today. He is an integral part of our team here at Oakwell and has been one of our most consistent performers for the last two seasons".