Kim, the third from his family to rule North Korea, read monotonously from a script in Pyongyang, calling for a push to "final victory".
The speech suggested Kim would stick to his father and grandfather's "military-first" policy. But the fact that he spoke at all was a surprise after years of silence from his father when he presided over similar events. Kim Jong-un inherited power when Kim Jong-il died in December.
He praised his grandfather and father as the "founder and the builder of our revolutionary armed forces". "Let us move forward to final victory," the twentysomething leader urged tens of thousands of military and civilians, who applauded throughout his speech of more than 20 minutes.
North Korea unveiled what appeared to be a new missile at the parade. Military analysts in Japan and South Korea said it appeared bigger than weapons previously displayed, but further examination would be needed to tell whether it was an intercontinental ballistic missile theoretically capable of reaching the continental US, which North Korea has reportedly been working on.
The celebrations came two days after North Korea fired a rocket widely viewed abroad as a provocative test of missile technology. The rocket failed about a minute after liftoff.