Haplochthoniidae is a small family within the superfamily Cosmochthonioidea and consists of only two genera and 17 species. In this paper a new species, Haplochthonius (Haplochthonius) longiapophysus sp. nov., is described and illustrated based on adult specimens sampled from soil in Sistan and Baluchestan province, southeastern Iran. The new species is characterised by very long prominent rostral apophyses; blade-like prodorsal and notogastral setae; genital plates with six and anal and adanal plates each with four pairs of setae, an₁, ad₁ and ad₂ thicker than other ano-adanal setae; epimeral setation 3-2-2-3; solenidion φ of tibiae I very long, solenidion ω of tarsi I longer than famulus, seta d longer than solenidion on tibiae II and III. The new species is morphologically very similar to Haplochthonius (Haplochthonius) sanctaeluciae Bernini, 1973, however, the most significant differences between them is in the morphology of rostral apophyses and number and size of genital setae. The family Haplochthoniidae is recorded for the first time from Sistan and Baluchestan province. An updated diagnostic key to the adults of known species of Haplochthonius (Haplochthonius) is given.