The pine wood nematode (PWN), Bursaphelenchus xylophilus, is able to produce hundreds of thousands of offspring in a short time. Its mating behaviour might play a basic role in this marked fecundity. We investigated the features of the mating behaviour of B. xylophilus using long-time microscope video and repeated observations. The mating behaviour of B. xylophilus could be separated into a series of sequential sub-behaviours, including cruising, approaching, encountering, touching, hooping, locating, attaching, ejaculating, separating, quiescence and roaming. Overall, the process of mating behaviour could be divided into four different phases, searching, contacting, copulating and lingering; the mean times for these different phases varied significantly with 21.8 ± 2.0 min, 28.0 ± 1.9 min, 23.6 ± 0.7 min and 7.2 ± 0.5 min for each of the four phases, respectively. Attraction between the sexes was observed, indicating that sex pheromone(s) might be involved in mating behaviour of B. xylophilus. In addition, when one female was placed with three males, male-male competition was observed, which might be caused by mating-choice pressure from the female. Intra-sexual competition of females was also occasionally observed.