"They will all be joining on two-year contracts," ESPN Cricinfo quoted Sri Lanka Cricket's CEO Ashley De Silva as saying.
Flower will be working with Sri Lanka's white ball teams and hence he would not travel to Pakistan for the upcoming Test series.
Arthur will now become the 11th head coach of Sri Lanka in the last eight years, and his first challenge would be to take on Pakistan in Pakistan.
He was the coach of Pakistan till the end of the World Cup this year. Pakistan sacked Arthur after a series of poor results.
However, Pakistan won the Champions Trophy under Arthur and it also attained the number one position in T20Is.
Saker has previously worked as a bowling coach for both England and Australia over the last ten years.
McDermott has earlier served as South Australia Cricket Association's high-performance coach.
Despite the new appointments, previous Sri Lanka head coach Chandika Hathurusingha remains under contract with SLC.