The rufous-capped spinetail is usually seen in pairs, and often joins mixed-species flocks (2) (4). Most foraging takes place in the understorey, with the prey, thought to be arthropods, probably gleaned from foliage and small branches, mainly within a metre or two of the ground (2). Like other members of the genus, this species often draws attention to itself by its frequently given vocalisations. The song of the rufous-capped spinetail is a fast, somewhat nasal di-di-di-di-reét, often repeated for long periods and often given between the members of a breeding pair (2) (4). The alarm call is a distinctive, low-pitched trill (2).
The rufous-capped spinetail is thought to be monogamous, and breeds during the spring and summer, building a relatively large nest of up to 40 centimetres in length. The nest is placed around 1 to 2.5 metres above the ground, amongst dense vegetation, and is constructed from a mass of sticks, which are usually thorny. The entrance is a tunnel which leads to the nest chamber. Clutch size is two to three eggs (2).