He joined Championship club Fulham on a three-year contract on 31 August 2015, with the fee undisclosed.

Fredericks made his Fulham debut, coming on as a substitute for Ben Pringle in the 62nd minute, in a 2–1 win against Blackburn Rovers on 13 September 2015.
He started out playing in the right–back position for the next two matches, before playing in the right–midfield position (whenever he came on as a substitute).
For the rest of the season, Fredericks continued to play in either the right–back position and right–midfield position.
Despite suffering injuries during the 2015–16 season Fredericks went on to make 36 appearances for Fulham in his first season.

In the 2016–17 season, Fredericks spent the start of the season with an ankle injury and was sidelined for between 10–12 weeks following surgery.
It wasn't until 18 October 2016 when he returned to the first team from injury, starting the match in the right–back position, in a 2–2 draw against Norwich City.
After returning from injury, he regained his first team place, in the right–back position.
In a match against Wolverhampton Wanderers on 10 December 2016, Fredericks played a role for Fulham when he set up two goals, resulting a 4–4 draw.
Seven days later, on 17 December 2016, he provided another assist in a match against Derby County, setting up a goal for Floyd Ayité, in a 2–2 draw.
Three weeks later, on 8 January 2017, Fredericks played another important role against Cardiff City in the third round of the FA Cup when he set up the equaliser, in a 2–1 win; his performance earning him the Man of the Match award.
However, in a match against Birmingham City on 4 February 2017, he was sent–off for a late tackle on Craig Gardner, in a 1–0 loss.
After serving a three match suspension, Fredericks immediately regained his first team place in the right–back position, where he stayed for the rest of the season.
He also played in both legs of the play-offs, which saw Reading win 2–1 on aggregate.
Throughout the season, Fredericks' performance was praised, due to his passing stats and pace.
By the end of the 2016–17 season, he had made 34 appearances in all competitions.

In the 2017–18 season, Fredericks continued to retain his first team place in the right–back position from the start of the campaign.
After going three league matches without a win, he then played a role when he set up a goal for Neeskens Kebano, in a 2–1 win over Ipswich Town on 26 August 2017.
Two weeks later, on 13 September 2017, Fredericks provided his second assist of the season, setting up the winning goal, in a 2–1 win over Hull City.
He was an ever present in the first team from the start of the 2017–18 season until he suffered a foot injury that saw him miss one game.
After returning from injury against Aston Villa on 21 October 2017, he regained his first team place.
His performances at Fulham attracted interest from clubs such as Swansea City and Stoke City, but stayed at the club throughout January.
His contributions led to Fulham reaching the play–offs and subsequently ended up gaining promotion to the Premier League after beating Aston Villa 1–0 in the final, where he started and played 83 minutes before being substituted.
For his seasons performances, Fredericks was named in the EFL Championship team of the year in April 2018, along with teammate Ryan Sessegnon and Tom Cairney.
He was also named in the Championship Team of the Season.
At the end of the 2017–18 season, Fredericks had made 48 appearances in all competitions.

With his contract at Fulham expected to expire at the end of the 2017–18 season, Fredericks hinted about staying at Fulham.
He joined Championship club Fulham on a three-year contract on 31 August 2015, with the fee undisclosed.
Fredericks made his Fulham debut, coming on as a substitute for Ben Pringle in the 62nd minute, in a 2–1 win against Blackburn Rovers on 13 September 2015. He started out playing in the right–back position for the next two matches, before playing in the right–midfield position (whenever he came on as a substitute). For the rest of the season, Fredericks continued to play in either the right–back position and right–midfield position. Despite suffering injuries during the 2015–16 season Fredericks went on to make 36 appearances for Fulham in his first season.
In the 2016–17 season, Fredericks spent the start of the season with an ankle injury and was sidelined for between 10–12 weeks following surgery. It wasn't until 18 October 2016 when he returned to the first team from injury, starting the match in the right–back position, in a 2–2 draw against Norwich City. After returning from injury, he regained his first team place, in the right–back position. In a match against Wolverhampton Wanderers on 10 December 2016, Fredericks played a role for Fulham when he set up two goals, resulting a 4–4 draw. Seven days later, on 17 December 2016, he provided another assist in a match against Derby County, setting up a goal for Floyd Ayité, in a 2–2 draw. Three weeks later, on 8 January 2017, Fredericks played another important role against Cardiff City in the third round of the FA Cup when he set up the equaliser, in a 2–1 win; his performance earning him the Man of the Match award. However, in a match against Birmingham City on 4 February 2017, he was sent–off for a late tackle on Craig Gardner, in a 1–0 loss. After serving a three match suspension, Fredericks immediately regained his first team place in the right–back position, where he stayed for the rest of the season. He also played in both legs of the play-offs, which saw Reading win 2–1 on aggregate. Throughout the season, Fredericks' performance was praised, due to his passing stats and pace. By the end of the 2016–17 season, he had made 34 appearances in all competitions.
In the 2017–18 season, Fredericks continued to retain his first team place in the right–back position from the start of the campaign. After going three league matches without a win, he then played a role when he set up a goal for Neeskens Kebano, in a 2–1 win over Ipswich Town on 26 August 2017. Two weeks later, on 13 September 2017, Fredericks provided his second assist of the season, setting up the winning goal, in a 2–1 win over Hull City. He was an ever present in the first team from the start of the 2017–18 season until he suffered a foot injury that saw him miss one game. After returning from injury against Aston Villa on 21 October 2017, he regained his first team place. His performances at Fulham attracted interest from clubs such as Swansea City and Stoke City, but stayed at the club throughout January. His contributions led to Fulham reaching the play–offs and subsequently ended up gaining promotion to the Premier League after beating Aston Villa 1–0 in the final, where he started and played 83 minutes before being substituted. For his seasons performances, Fredericks was named in the EFL Championship team of the year in April 2018, along with teammate Ryan Sessegnon and Tom Cairney. He was also named in the Championship Team of the Season. At the end of the 2017–18 season, Fredericks had made 48 appearances in all competitions.
With his contract at Fulham expected to expire at the end of the 2017–18 season, Fredericks hinted about staying at Fulham.
Ryan Fredericks