"Whilst this news has come as a shock, I have many reasons to be positive. I am receiving the best possible care from my clinicians, and have the love, support and prayers of my family.

"I have never been afraid to fight the battles that need fighting, and this is no exception."

Hailing from the Eden-Monaro electorate, the news was concerning for many.

Especially after the positive announcement that he and Wife Anna also celebrated their 49th year of marriage over the Easter long weekend.

Member for Eden-Monaro Kristy McBain shared her well wishes on social media.

"All the best Jim, see you back on the hill soon."

Prime Minister Scott Morrison also shared his support for the Senator in a response tweet to the Senator's official statement.

"We've worked together for over a decade now and you've always put your service above all else.

"You are an incredible person. We will all be here to support you through this battle ahead."

Senator Molan joins fellow government members Christian Porter, Linda Reynolds and Andrew Laming on different forms of leave ahead of federal parliament next sitting in mid-May.

The senator said his NSW electoral office will remain open and fully operational, and that his team will continue to work hard alongside his colleagues in the Morrison government.

The Senator thanked everyone for their support and asked for privacy during this time.

His term is not due to expire until mid-2022.