The note was sent in response to congratulations from Kim Jong-un last week for securing a second term as the head of China's ruling party.
"I wish that under the new situation the Chinese side will make efforts with the DPRK to promote relations between the two parties and the two countries to a sustainable soundness and stable development," Xi said, according to North Korea’s KCNA news agency, addressing Kim as "Comrade Chairman.”
In a regular press briefing in Beijing on Thursday Chinese foreign ministry spokeswoman Hua Chunying said that the message from the North Korean leader was just one among many others received. Xi had responded "out of politeness," she said.
The last time KCNA reported a message from Xi was in July 2016.
Although Beijing and Pyongyang have exchanged greetings and congratulated each other on key anniversaries in the past, in recent times such exchanges have become very rare due to political tensions in the region.
Beijing has backed a new set of UN measures after North Korea launched a number of sporadic missiles and conducted its sixth nuclear test in September.