The lack of clarity over his future after discussions with the Sri Lankan board was reportedly the prime reason behind Arthur's decision to step down.
Arthur announced his decision to move on as coach of the national team in an e-mail to the top brass of the board.
He also mentioned that while he wishes to continue in his current capacity, it is difficult for him to keep going without any assurances over his future. Arthur wrote in his email:
"I just wanted to inform you that with regret and against my preferred option I have signed a 3-year contract as Director of Cricket with Derbyshire County Cricket Club to commence after my last assignment being the Test series against West Indies."
"All I wanted was an indication from SLC that you were happy with the job that myself and my very loyal and good support staff were doing and I would have stayed, having not received anything I felt with no option. I have fallen in love with Sri Lanka Cricket, the players, the people and your beautiful country."
Arthur was appointed as the head coach of the Sri Lanka national team in February 2020, during a crucial phase. This marks the fourth country he has coached following stints with South Africa, Australia and Pakistan.
Leaving Sri Lanka in a much better place: Mickey Arthur
The island nation endured a very tough transition phase following a string of senior player departures. Arthur has played a vital hand in planting the seeds of a potential resurgence with several promising young players breaking into the first team.
"I know that Sri Lanka is a far better place than when I arrived and have helped groom some very good talent as well as developing a team and brand that can give SLC some sustainable success in the future."
He also assured the board that despite his tenure coming to an end, his focus will remain on the Test series against West Indies.
"I am determined beyond no end to help the players beat the West Indies in the last series and would like nothing better to sign off with a Test series win."
Sri Lanka will host the West Indies for a two-match Test series starting on November 21. Both Tests will be hosted at the Galle International Stadium.