Kim had stirred heated controversies last year when he skipped his New Year speech – which usually provides insights into his administration's plans for the year.
North Korean President, Kim Jong-un, has appreciated citizens of the country for backing his leadership during "difficult times" in a rare New Year message.
The letter, released on Friday, comes ahead of a crucial ruling party congress that will set the country’s economic goals.
It also comes shortly after a New Year celebration in North Korea amid the coronavirus pandemic which the country has consistently said has yet to reach its shores.
Kim had stirred heated controversies last year when he skipped his New Year speech – which usually provides insights into his administration's plans for the year – in January 2020.
The North Korean leader is expected to drop the televised speech again this year ahead of the country’s first congress in five years billed for early January, according to state media.
“I sincerely wish all the families across the country greater happiness and beloved people, good health,” Kim said in the letter carried by the official Korean Central News Agency.
“In the new year, too, I will work hard to bring earlier the new era in which the ideals and desires of our people will come true.
“I offer thanks to the people for having invariably trusted and supported our party even in the difficult times,” he added, apparently referring to economic hardship brought by international sanctions and strict anti-coronavirus measures.
According to South Korean media, the development marks the first time since 1995 that a North Korean leader has sent a New Year card to the country’s citizens, the last one coming from Kim’s father, Kim Jong Il.
The country's forthcoming congress is scheduled to take place ahead of the January 20 inauguration of Joe Biden as US president.
Relations with the United States have been deadlocked since talks between President Donald Trump and Kim stalled early last year.