The terms of Dunn’s contract were not immediately available.
The Browns also waived tight end Nate Wieting.
Five Browns players have opted out of the 2020 season because of concerns related to the coronavirus pandemic: Guards Drew Forbes, Colby Gossett and Malcolm Pridgeon, undrafted rookie offensive tackle Drake Dorbeck and defensive tackle Andrew Billings.
Thursday afternoon marked the deadline for players to opt-out.
Players who opted out for approved medical reasons will receive a $350,000 stipend for 2020 and not advance against future salary.
Other players who opted out for other COVID-19 concerns will receive a $150,000 for the season, which is treated as a salary advance and come out of future years’ pay unless the player is an undrafted rookie.
Dunn’s signing gives the Browns some depth behind Wyatt Teller, who is expected to be the favorite to win the starting right guard position.
Starting left guard Joel Bitonio is the only other guard listed on the Browns’ roster.
Browns general manager Andrew Berry and the team’s front office could continue to add offensive line depth with last week’s opt-outs.
As of Sunday afternoon, OverTheCap.com shows the Browns still have $40.59 million in salary-cap space.
Dunn, 25, was a member of the XFL for the Seattle Dragons earlier this year.
In 2019, Dunn played in the now-defunct Alliance of American Football for the Birmingham Iron.
Dunn also played for the Miami Dolphins in the 2019 preseason.
The 6-foot, 315-pound guard was a practice-squad member of the Los Angeles Rams (2017) and Jacksonville Jaguars (2018).
In 2017, Dunn signed with the Rams as an undrafted free agent out of Maryland.
Dunn started 48 career college games, earning All-Big Ten honorable mention in 2015 and 2016.
Entering his fourth professional season, Dunn has yet to appear in an NFL regular-season game.
Wieting, 23, signed with the Browns as an undrafted free agent out of Iowa earlier this spring.
In 2019 for the Hawkeyes, Wieting had 11 receptions for 117 yards.
Wieting was hampered by shoulder, knee and foot injuries during his college career.