The present study reports for the first time on the behavior prior to, during and after the copulation of a member of the haplogyne spider family, Tetrablemmidae and describes the web of this species. Prior to copulation, male and female of Indicoblemma lannaianum from Thailand sometimes avoided each other or the female scared the male away, apparently by vigorous vibrations of her body. When first copulations were initiated, they lasted from 1.21 to 3.8 h with an average of 2.25 ± 0.71 h (n = 17). Some females accepted a second male for mating 3–9 days after first mating. There was no significant difference between the duration of first and second copulations but significantly more trials were needed to induce the second copulations. In the copulatory position, the male was inverted and faced in the same direction as the female. He seized the female's opisthosoma with apophyses on his chelicerae which fit into grooves on a female's ventral plate in this way building a locking mechanism during copulation. The pedipalps were inserted alternately. The web of I. lannaianum consisted of a longish narrow sheet, which was made of many short threads forming a zigzag pattern and additional long oblique threads overdrawing the sheet and functioning as signal threads.