"In testing times, we often observe that the best of the human spirit comes to the fore; the dedication to service of countless nurses, midwives and other health workers, in these most challenging circumstances, is an example to us all.
"My family and I send our enduring appreciation and good wishes," she added.
The Queens congratulatory letter comes just two days after she addressed the United Kingdom in a video on Sunday, where she gave thanks to all essential workers.
Taking to YouTube on Sunday, Her Majesty addressed the nation while wearing an elegant green frock embellished with a spectacular diamond and turquoise brooch.
The brooch was originally gifted to Queen Mary in 1893 as a wedding present from her in-laws, the future King Edward VII and Queen Alexandra, before it was given to Elizabeth.
“I am speaking to you at what I know is an increasingly challenging time,” the Queen began. “A time of disruption in the life of our country: a disruption that has brought grief to some, financial difficulties to many, and enormous changes to the daily lives of us all.”
Her Majesty then gave a shout out to NHS front line heathcare workers, as well as care workers and those carrying out essential roles to support the United Kingdom.
“I am sure the nation will join me in assuring you that what you do is appreciated and every hour of your hard work brings us closer to a return to more normal times,” she added.
“I also want to thank those of you who are staying at home, thereby helping to protect the vulnerable and sparing many families the pain already felt by those who have lost loved ones,” she said.