The Jaguars announced Thursday that Harrison was sent to the Browns in exchange for a 2021 fifth-round draft pick.
Harrison becomes the third Jaguars starter in the past five days to be traded or released. The team shipped disgruntled defensive end Yannick Ngakoue to the Minnesota Vikings on Sunday and waived star running back Leonard Fournette on Monday.
The Browns were in need of a safety after second-round pick Grant Delpit suffered a season-ending Achilles injury in training camp Aug. 24.
The Jaguars selected Harrison in the third round of the 2018 NFL Draft out of Alabama. Since 2016, he is the third player drafted by the Jaguars in the first three rounds to be released or traded before playing out his rookie deal -- joining cornerback Jalen Ramsey and Fournette.
Harrison started 22 of the 28 games in which he played for the Jaguars. He has recorded 103 total tackles, three sacks, three interceptions, one fumble recovery and 12 passes defensed in his NFL career.