The singer was diagnosed with stage three malignant melanoma in 2016 and subsequently began immunotherapy in March 2017.
In one of the last social media posts before his death, the singer returned to his home in Cork, Ireland, and was delighted to be taking a trip down memory lane.
In a separate message, the former X Factor victor wrote: "So sad to hear the news of @the_overtones singer Timmy Matley passing away this week!"
They said: "It is with the greatest sadness that we have to announce that our dear friend and brother Timmy has passed away". 'We know this news will be as heartbreaking for you all as it is for us.
In 2016 the group toured with stage show That's Entertainment and then A Christmas Tour later that year, but Timmy was forced to pull out after his skin cancer diagnosis.
"Timmy was 36 and was a lovely guy whose journey from Liam Healy Road in Cork took him to London and the great stages of success that he enjoyed with The Overtones".
"Heaven has gained the most handsome angel".
Fans have since paid tribute to the talented singer across social media, among then TV presenter Phillip Schofield and former X Factor victor Sam Bailey.
"He was such a lovely and talented man. In total shock. Sleep tight Timmy".
The five-piece band originally formed in 2010 and were originally called DYYCE.
He was planning to take part in a fundraising skydive next month to support The Royal Marsden Cancer Charity, an organisation he said was "very close to my heart".
They went on to have four top 10 albums in the United Kingdom, with their debut studio album Good Ol' Fashioned Love reaching number 4. To his Mam Geraldine and Sister Audrey, the heartfelt sympathy from Jonathan and myself.
Immunotherapy pauses the growth of cancer in order to allow your own immune system to fight the disease and has proved the most effective treatment for this type of cancer.