Quinn stood and raised his right fist, as he did during the anthem last season with the Rams.
Philadelphia Eagles safety Malcolm Jenkins resumed his protest against social inequality by raising his fist during the national anthem prior to Thursday's preseason opener against the Pittsburgh Steelers.
There also were at least two players who took a knee during the playing of the national anthem.More news: Malaysia's Najib pleads not guilty to money laundering as charges pile up
Kaepernick applauded the Dolphins players shortly after the display for their protest of "systemic oppression". Teammate Chris Long reportedly "placed his arm around Jenkins' shoulder" during the song.
There were no other actions by either Seattle or Indianapolis players during the performance of anthem.
In July, the NFL chose to suspend its new anthem policy which required all players on the field to stand for the national anthem.
The debate ratcheted up a notch in 2017 when US President Donald Trump said kneeling players showed "total disrespect for our great country".
Eagles defensive end Michael Bennett, a frequent protestor previous year when he played for the Seattle Seahawks, walked out of the tunnel as the anthem played. The three players - Quinton Jefferson, Branden Jackson and Duane Brown - quickly ran out to join the team after the anthem was complete. In July, the league and players association jointly announced that the new rule was "frozen" until further notice.