Treatment of blood blister-like aneurysm (BBA) is a challenge due to its unfavourable morphology, small size and the friable neck of BBA. In the management of ruptured BBA, coil placement can be achieved by stent-assisted coil embolisation. We propose to incorporate a new technique using a steam-shaped microcatheter to improve safety. A 59-year-old woman was transferred to our hospital and diagnosed with subarachnoid haemorrhage (SAH) due to a ruptured BBA of the left internal carotid artery (ICA) at the C2 portion. For coil embolisation, we selected the aneurysm sac using a three-dimensional shaping technique and the jailing method. Post-embolisation angiography revealed complete occlusion of the aneurysmal sac. For safe treatment and stability of BBA, the shape of the catheter tip and the distal portion of the microcatheter are two important factors to consider. The proposed technique could help resolve the problem of catheter shaping in the treatment of BBA.