Kim, who skipped his annual New Year's speech but has vowed military countermeasures against rival powers at the end of the year, was seen with his wife, Ri Sol Ju, on KCTV, in images reminiscent of founder Kim Il Sung, South Korean news service News 1 reported.
The documentary included all three leaders, including Kim's father Kim Jong Il, visiting Mount Paektu during different historical periods. The footage may have been carefully curated; each leader could be seen sitting by a campfire with subordinates. In one excerpt, Kim Jong Il is seen sharing roasted potatoes with comrades.
The documentary lasted about an hour, according to Yonhap news agency. North Korean leaders have traditionally visited Mount Paektu ahead of important decisions; analysts have said North Korea could undertake more serious weapons tests in 2020, including the test launch of an intercontinental ballistic missile.
The film that aired on Thursday may have included a criticism of members of North Korea's younger generation who have no memory of founder Kim Il Sung.
"New generations that have not undergone the trials of revolution have emerged as the main force" at present, the North Korean documentary narrator says, quoting Kim Jong Un. "This is at a time when imperialists and class enemies are trying to tear apart our ideological, revolutionary and national positions.
"We must always live and struggle by the ideology of the Mount Paektu attack."
Mount Paektu is a symbol of anti-colonial resistance in the North.
Kim has rejected diplomatic engagement with the United States and South Korea. On Thursday Seoul said it maintains "belief" in U.S.-North Korea dialogue, according to Newsis.
Foreign Minister Kang Kyung-wha said the U.S.-South Korea alliance should be the foundation for a "diversified diplomacy" between the two countries in addition to Japan, China and Russia, according to the report.