Female players could previously acquire this outfit by choosing the save for up for a costume option from a random event gift box (from the Frogs random event) then getting a piece of the costume from Thessalia in Varrock. It is now purchasable from Iffie's Random Costume Shop. It should be noted that only a female character may wear the princess outfit. If gender is changed whilst wearing it (going to the Makeover Mage) then the outfit will change into a prince outfit, the male equivalent, which is obtained in the same way. If the player changes their gender and attempts to wear the outfit of the opposite gender, it will say that the piece of clothing magically changes into the opposite gender's equivalent.
Before the random event gift was released; it was possible to exploit a glitch that causes the system to recognise a gender change and change it to a Prince outfit, but the colours of the Princess outfit remained. This has since been fixed by Jagex.