Along the Karakorum Highway (KKH), the key route for the China-Pakistan Economic Corridor, there are many rockfalls and unstable slopes, usually caused by tectonic movement and rainfall on the fractured rocks and slopes. This paper presents a numerical investigation of the rockfall and slope stability along the Karakorum Highway in Jijal-Pattan, Northern Pakistan using DIPS, GeoRock 2D and SLIDE, focusing on rockfall and slope stability along the KKH to develop countermeasures. Along the KKH, two major sections susceptible to rockfalls were selected to investigate the mechanism of rockfall and slope instability. The stereographic projection analysis following four sets of joints indicates that both sections are prone to plane failure and wedge failure. Based on the limit equilibrium theory, under static loading, the slope for Section 1 showed a stability coefficient of 0.917, representing its instability, and the slope in Section 2 has a stability coefficient of 1.131 depicting its slight stability. However, under the seismic condition, the stability coefficients of the slopes were lower than 1 for both sections, which indicates their instability. The results by GeoRock 2D reveal that in Section 1 the fallen rock mass attained the bounce height of 33 m, and in Section 2 it attained a bounce height of 29 m. The fallen rocks in Section 1 have the total kinetic energy of 1 135.099 kJ with a velocity ranging from 0.5 m/s to 44 m/s, while in Section 2 the fallen rocks have a velocity ranging from 0.5 m/s to 40.901 m/s with a damage capacity of 973.012 kJ. This study showed the rockfalls and landslides along the KKH have great damage potential.