A patient with bilateral aniridia and progressive congenital cataract was treated at the age of 7 years through phacoaspiration with femtosecond laser capsulotomy, in-the-bag intraocular lens implantation, and pars plana vitrectomy (combined with posterior capsulotomy). The diameter of the planned anterior capsulotomy was 4.7 mm; however, due to elevated tension in the young capsular bag, the capsulotomy diameter increased (to around 6 mm) shortly after release of the tension by the laser. In addition, the patient had a very flat and small cornea, causing the formation of air bubbles in the curved laser interface. This was addressed by filling the gap by using a viscoelastic. A very similar situation was observed in both eyes. Use of the femtosecond laser facilitated a successful outcome in a complex congenital cataract case with a safe capsulotomy that ensured in-the-bag intraocular lens placement.