Joseph-Day attended and played college football for Rutgers University from 2013 to 2017 under head coaches Kyle Flood and Chris Ash.[4][5] In the 2013 season, he appeared in one game, which came against Norfolk State, and recorded one tackle. He ended up redshirting after suffering an injury.[6] In the 2014 season, he appeared in three games and recorded three total tackles on the season.[7] He saw an expanded role in the 2015 season. He appeared in 11 games and recorded 22 total tackles, 5.5 tackles-for-loss, one sack, and one fumble recovery.[8] In the 2016 season, he appeared in 11 games and recorded 29 total tackles, 3.5 tackles-for-loss, one sack, one pass defensed, and one forced fumble.[9] In his final collegiate season, in 2017, he appeared in 11 games and recorded 35 total tackles, 4.5 tackles-for-loss, 1.5 sacks, one pass defensed, and one forced fumble.[10]
After being inactive for every game as a rookie, Joseph-Day was named a full-time starter in 2019.[15] In the 2019 season, he finished with two sacks, 44 total tackles, and one pass defended.[16] In the 2020 season, he finished with one sack, 55 total tackles, three passes defended, and one forced fumble.[17]
On November 5, 2021, Joseph-Day was placed on injured reserve after undergoing surgery for a torn pectoral.[18] He finished the 2021 regular season with three sacks and 38 total tackles in seven games.[19] He was activated off injured reserve on February 11, 2022, in time for Super Bowl LVI.[20] The Rams won 23–20 against the Cincinnati Bengals.[21]
Los Angeles Chargers
On March 16, 2022, Joseph-Day signed a three-year, $24 million contract with the Los Angeles Chargers.[22] In Week 7, against the Seattle Seahawks, he recorded a safety when he and teammate Troy Reeder tackled Kenneth Walker in the end zone.[23] On December 7, Joseph-Day was diagnosed with an MCL sprain.[24] In the 2022 season, he appeared in 16 games. He finished with two sacks, 56 total tackles, one interception, one pass defended, and one forced fumble.[25] On December 22, 2023, he was cut by the Chargers.[26]
San Francisco 49ers
On December 27, 2023, Joseph-Day signed with the San Francisco 49ers.[27] He was a member of the 49ers team that appeared in Super Bowl LVIII in February 2024, representing his second Super Bowl appearance during his NFL career to date.
Tennessee Titans
On March 20, 2024, Joseph-Day signed with the Tennessee Titans.[28] He appeared in all 17 games during the 2024 season, including 12 starts. He finished with 44 tackles, 2.5 sacks, and a pass deflection.[29]
Joseph-Day is a Christian.[30] He is married to Rachel Joseph-Day.[31] They have one son.[32]
Joseph-Day appeared with Mike Tyson as a fill-in co-host on his podcast "Hotboxin' with Mike Tyson".[33] The opportunity to continue co-hosting was offered and accepted.[34] Joseph-Day hosts a restaurant tour series on his YouTube channel called "Dine n' Bash".[35] In July 2021, he launched a charitable initiative called "Bashing Hunger."[36] The effort is designed to combat food insecurity by raising awareness of the issue, increasing food rescue to feed people without enough food, and providing nutritional education.[37]
