Walker said: “Sussex is a club I have always admired and one with a proud history. The opportunity to work with this group of players and staff, alongside Paul [Farbrace], was one that really excited me.
“There is already a strong foundation in place and I’m looking forward to building on that as we strive to help Sussex compete for trophies. I can’t wait to get started.”
Farbrace said Walker possessed the “experience, energy and enthusiasm” that the club had been looking for.
“I’m really looking forward to working alongside him as we tackle the challenges in front of us and build a team capable of competing for trophies,” he added.
Sussex returned to Division One as champions in 2024 under the guidance of Farbrace, before finishing fourth in 2025.
The club were then hit with a 12-point deduction for the 2026 season after “sustained operating losses” in the previous financial year.
Walker and new club chairman Ed Warner will have to work within tight financial restrictions going forward.
The club is under a player salary cap until 2028, and need to provide the ECB with a three‑year business plan, and deliver sustainable year‑on‑year operating profits for the same period.
Young fast bowler Henry Crocombe is joining Surrey in 2027, and BBC Radio Sussex understands that John Simpson, Tom Clark, Fynn Hudson-Prentice, Danny Lamb and Charlie Tear are all out of contract at the end of the season.
Sussex interim chief executive officer, Mark West, said the revamped management team would be key to the club turning the corner following their recent financial problems.
“Matt’s appointment is another important step for Sussex Cricket as we continue strengthening the club both on and off the field.
“He is joining a talented group of players and staff, and we believe he is the right person to help drive the next phase of our cricket programme”.