The 3 September 2017 nuclear test conducted by the Democratic People’s Republic of Korea was followed by a series of small seismic events. In this study, we conduct a survey of small seismic events from 1 May 2017 to 25 April 2018 near North Korea’s nuclear test site. We report 88 seismic events, including the 2017 nuclear test, the collapse event 8.5 min later, and 86 earthquakes afterward. Among the 86 earthquakes, 11 are well constrained to be distributed along a near north–south direction within a region of 2 km, north of the test site. The null detection before the 2017 test and the intense seismicity after the test, along with the predicted normal tensile stress the 2017 test applied on the fault, provide strong evidence that the 2017 test triggered these earthquakes. Some characteristics (the distance to the nuclear test center, depth, and magnitude) of these triggered aftershocks fit the general characteristics of the aftershocks in the Nevada National Security Site and the Semipalatinsk test site after nuclear tests, but the aftershocks of North Korea’s 2017 test exhibit a different evolution lasting at least eight months with two bursts occurring on early December 2017 and early February 2018 and an otherwise general low occurrence rate, possibly caused by a different geological setting of the test site.