Spirocamallanus olseni is a small worm with a thick, finely striated cuticle. Males are smaller than females, with males having shorter and narrower bodies. The female body is longer and slightly wider. The buccal capsule is brown and features two sets of spiral thickenings, with 22 in each set. In males, the buccal capsule is barrel-shaped and smaller compared to the chitinous buccal capsule in females. Both lack tridents. The oesophagus has a muscular part that is shorter in males than in females, while the posterior glandular part is longer in males. Males have two unequal and dissimilar spicules, with the right spicule being longer than the left.